The Prevalence of Behavioural Symptoms and Psychiatric Disorders in Hadza Children

doi:10.21203/rs.3.rs-2471516/v1

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The Prevalence of Behavioural Symptoms and Psychiatric Disorders in Hadza Children

https://doi.org/10.21203/rs.3.rs-2471516/v1

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published 12 Dec, 2023

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73.9% of all psychiatric disorders start before the age of 18. Studying the prevalence of childhood psychiatric disorders across radically different economic systems and social structures could indicate universal factors leading to their development. We compared the prevalence of behavioural symptoms and psychiatric disorders in Hadza children (n=113), a mixed-subsistence foraging group, to a nationally representative sample from England (n=18,029) using a cross-sectional study design. Emotional problems, conduct problems and hyperactivity were lower in the Hadza children. Prosocial behaviour and peer problems were higher in Hadza children. 3.6% of Hadza children met the criteria for a psychiatric disorder compared to 11.8% in English children. All psychiatric disorders in Hadza children were co-morbid with autism spectrum disorder. No child from the Hadza group met the criteria for an emotional, behaviour or eating disorder. Further work should study the factors which lead to lower rates of psychiatric disorders in Hadza children.

Health sciences/Diseases/Psychiatric disorders/Addiction

Health sciences/Diseases/Psychiatric disorders/Adhd

Health sciences/Diseases/Psychiatric disorders/Anxiety

Health sciences/Diseases/Psychiatric disorders/Autism spectrum disorders

Health sciences/Diseases/Psychiatric disorders/Bipolar disorder

Health sciences/Diseases/Psychiatric disorders/Depression

Health sciences/Diseases/Psychiatric disorders/Obsessive compulsive disorder

Health sciences/Diseases/Psychiatric disorders/Post traumatic stress disorder

Health sciences/Diseases/Psychiatric disorders/Psychosis

Health sciences/Diseases/Psychiatric disorders/Schizophrenia

Psychiatric disorders in children and adolescents are common, treatable, and growing in prevalence in England [1]. Recent evidence demonstrates that three out of four people will experience mental health problems during their lifetime [2]. 73.9% of all psychiatric disorders start before the age of 18 [3], with the peak onset at 14–15 years. The onset of psychiatric disorders involves complex interactions between genetic [4], cognitive, environmental and societal factors [5] [6] [7] but there is little agreement about the necessary or sufficient conditions to cause psychiatric disorders. One theory is based on the concept of evolutionary mismatch, where some psychological mechanisms originally used to solve problems in ancestral environments are maladaptive in modern societies [8]. It is impossible to draw direct conclusions about the prevalence and causation of psychiatric disorders in environments such as pre-agricultural societies. However studying the prevalence of psychiatric disorders across radically different economic systems and social structures could indicate universal factors leading to their development. Little is known about the prevalence of these disorders in low and middle-income countries, and the prevalence of psychiatric disorders in people living in a mixed-subsistence foraging social structure is entirely unknown.

The Hadza are an indigenous ethnic group of mixed-subsistence foragers residing in Northern Tanzania in a savannah woodland habitat south of the Serengeti. The total population of the Hadza is approximately 1000–1500 individuals, with approximately 300–400 children. Calculating the exact number of Hadza children is difficult, as no full census has been carried out, and records of birth dates are sparse. Nearly all the population reside around the shores of Lake Eyasi. Historically, the Hadza have largely subsisted by practicing a hunter-gatherer lifestyle. It is impossible to tell how representative this group is of ancestral cultural and social systems. However, they operate an economic system and social organisation which is radically different to those seen in agricultural societies, and is relatively closer to living conditions in the Paleolithic era than contemporary Western populations [9]. Factors such as income from tourism, contact with neighbouring social groups and engagement with researchers limits the ability to make inferences about life in pre-agricultural societies.

While no known contemporary foraging population relies exclusively on wild foraged food, before the coronavirus pandemic there were approximately 150–300 Hadza individuals who continued to consume a diet primarily composed of wild foods [10]. This number has increased substantially in the last two years as the income derived from tourism has dwindled. All members of the Hadza ethnic group speak Hadzane as their first language and almost all Hadza above the age of 8 years old speak Swahili as their second language. Swahili is the language used between different ethnic groups living in the area, between the Hadza, governmental bodies and non-governmental aid organisations, as well as the language that is mainly used by researchers. Hadza who reside in camps have a diet mainly composed of wild foods but also includes domesticated products such as maize—mainly consumed as dietary supplements. Sharing food starts early in life and forms an important aspect of Hadza culture [11]. Hadza have a lack of access to health care services, including reproductive healthcare. This manifests as high levels of maternal and infant mortality [12][13]. The majority of Hadza bush camps are located considerable distances from any hospitals or clinics, and mental health facilities are out of reach for most Hadza.

There have been previous studies attempting to understand aspects of mental health and wellbeing of the Hadza. The mental health of postpartum females of Hadza mixed-subsistence foragers has been studied in one previous study [14]. In addition, the Hadza perception of emotions has been studied [15]. There is a large body of work in medical anthropology detailing problems with applying universal diagnostic methodologies and treatments wholesale across populations [16]. However, no studies have compared the prevalence of paediatric behavioural symptoms and psychiatric disorders in mixed-subsistence forager societies versus Western ones. We aimed to investigate the prevalence of paediatric behavioural symptoms and psychiatric disorders in the Hadza population, compared to a nationally representative sample from England, an agricultural society. We hypothesised that the wide differences in important economic, social and cultural factors in Hadza society compared to English society would lead to different prevalence rates of childhood psychiatric disorders.

Population sample

The overall population sample comprised 140 children and young people from the Hadza tribe. Sociodemographic data were collected for 107 of these children and are presented in Table 1. The sample ranged in age from 3 to 17 years with a median age of 8 years (interquartile range (IQR)= 5 to 11 years) and 53.3% of the sample were female (n=57). In terms of living status, 70.1% of children reported living with their mother, and 59.8% reported living with their father. 45.8% of the children lived in the Domanga camp, 23.4% lived in the Gideru camp, 14.0% lived in the Sengele camp, and 16.8% lived in the Ukumako camp. 29% of children had received or were receiving education with a median education duration of 4 years (IQR=2 to 6 years). No children consumed alcohol regularly, but 5.6% reported using tobacco and 3.7% reported using marijuana. Three children (2.8%) had a physical disability and three had psychological problems according to the Development and Well-Being Assessment (DAWBA).

A subsample of Hadza children aged 5-16 years (n=113) was created to facilitate comparison with data from the Mental Health of Children and Young People 2017 (MHCYP). Sample characteristics are provided in Table 1 for those children that sociodemographic data were collected for (n=83) and were similar to those reported for the overall sample. Not all participants who completed an Strengths and Difficulties Questionnaire (SDQ) had a completed DAWBA.

Mental health of Hadza children and MHCYP comparator groups

SDQ scores for the overall sample (n=140), the subsample aged 5-16 years (n=113), and for 5-16-year-olds from MHCYP 2017 (n=2588) are presented in Table 2. As inferential statistics were not possible due to the summary nature of the MHCYP data, descriptive comparisons were made between 5-16-year-olds from the Hadza tribe and 5-16-year-olds from the MHCYP which are presented in Figure 1.

Children from the Hadza tribe (M=7.1, 95% CI=6.3 to 8.0) had lower levels of total difficulties compared to children from MHCYP (M=8.0, 95% CI=7.7 to 8.4). However, as the confidence intervals overlap it is unlikely that this difference was statistically significant. Levels of emotional problems (Hadza: M=1.3, 95% CI=0.9 to 1.6; MHCYP 2017: M=2.1, 95% CI=2.0 to 2.2), conduct problems (Hadza: M=0.6, 95% CI=0.4 to 0.8; MHCYP : M=1.4, 95% CI=1.3 to 1.5) and hyperactivity (Hadza: M=2.5, 95% CI=2.1 to 2.9; MHCYP 2017: M=3.1, 95% CI=3.0 to 3.3) were lower in the Hadza children, and levels of prosocial behaviour (Hadza: M=9.4, 95% CI=9.1 to 9.7; MHCYP 2017: M=8.7, 95% CI=8.6 to 8.8) were higher, compared to children in MHCYP 2017. However, peer problems appeared to be higher among Hadza children (Hadza: M=2.8, 95% CI=2.6 to 3.0; MHCYP 2017: M=1.4, 95% CI=1.3 to 1.5). On all SDQ subscales, confidence intervals did not overlap between Hadza children and children from the MHCYP indicating that these differences are likely to be statistically significant.

Prevalence of mental disorders of Hadza and MHCYP comparator groups

From the Hadza dataset, DAWBA data were available for 61/80 children aged 5-10, and 22/33 children aged 11-16. 3.6% (n=3) of children from the Hadza 5-16 year old subsample met the criteria for any psychiatric disorder, compared to 11.8% in the comparable age group from MHCYP. All Hadza children with psychiatric disorders in the 5-16 year sample were girls and all were from the 5-10 year old age group. All other psychiatric disorders diagnosed in Hadza children were comorbid with autism spectrum disorder (ASD). No children from the Hadza 11-16 age group met the criteria for a psychiatric disorder, compared to 14.4% in the comparable age group from MHCYP.

Regarding emotional disorders, no child from the Hadza met the criteria for an emotional disorder. In the MHCYP data, 4.1% of children aged 5-10, and 9.0% of children aged 11-16 met the criteria for a emotional disorder.

No child from the Hadza met the criteria for a behavioural disorder. In the MHCYP data, 5.0% of children aged 5-10, and 6.2% of children aged 11-16 met the criteria for a behavioural disorder.

No child from the Hadza met the criteria for an eating disorder. In the MHCYP data, 0.1% of children aged 5-10, and 0.6 % of children aged 11-16 met the criteria for an eating disorder.

4.9% of Hadza children aged 5-10 met the criteria for ASD, compared to 1.5% of 5-10 year olds in MHCYP 2017. No Hadza children aged 11-16 met the criteria for ASD, compared to 1.2% of the same age group in MHCYP 2017.

The number of Hadza children with mental disorders was too small to be able to conduct meaningful statistical analysis, however here we provide a narrative description for illustrative purposes:

Child 1 was a female aged 6 and met the criteria for ASD. She displayed high emotional difficulties, close to average conduct problems, high hyperactivity problems, high peer problems, very low prosocial strengths, and her total difficulties score was very high.

Child 2 was a female aged 6 and met the criteria for ASD, hyperkinetic disorder, Rett’s syndrome, social phobia, and motor tics. She displayed very high emotional difficulties, high conduct problems, very high hyperactivity problems, close to average peer problems, very low prosocial strengths, and her total difficulties score was very high.

Child 3 was a female aged 10 and met the criteria for ASD, social phobia, and Tourette syndrome. She displayed very high emotional difficulties, very high conduct problems, slightly raised hyperactivity problems, high peer problems, very low prosocial strengths, and her total difficulties score was very high. We also noted she had characteristic clinical features of Down syndrome.

Child 4 was a male aged 4 and met the criteria for ASD and hyperkinetic disorder. He displayed close to average scores for emotional problems, conduct problems, hyperactivity, prosocial strengths and total difficulties. He displayed high peer problems scores.

Gender differences in positive and negative behavioural symptoms (SDQ scores)

Looking at boys and girls separately (see Table 2) revealed that differences in SDQ scores between Hadza children and English children were much more pronounced in boys. Boys from the Hadza tribes (compared to boys from MHCYP 2017) appeared to have significantly (confidence intervals do not overlap) lower total difficulty scores, lower levels of emotional and conduct problems, lower levels of hyperactivity, and higher levels of prosocial behaviour. However, peer problems were higher in boys from the Hadza tribe.

Overlaps in confidence intervals suggest that girls from the Hadza tribe did not differ significantly from girls in England in total difficulty scores, levels of hyperactivity, and levels of prosocial behaviour. However, they had lower levels of emotional and conduct problems, and higher levels of peer problems when compared with children in MHCYP 2017.

Associations between sociodemographic factors and SDQ scores in Hadza children

We examined associations between age, sex, camp, and living status (living with father, living with mother) and SDQ scores in in the overall sample (aged 3-17 years, n=107) from the Hadza tribe. There was no evidence that age was associated with total SDQ scores or any SDQ subscale (all p values >0.05). Sex was not associated with any SDQ score apart from prosocial behaviour (β=-0.66, 95% CI=-1.19 to -0.13) where boys (M=9.94, SD=0.31) had significantly higher levels than girls (M=9.28, SD=1.88).

Summary SDQ scores for each Hadza camp are provided in Table 3 to facilitate comparison. Compared to children from the Domanga camp, children from Gideru camp had significantly lower total difficulty scores (β=-3.17, 95% CI=-5.03 to -1.31), whereas scores for the children from the Sengele camps were significantly higher (β=2.30, 95% CI=0.07 to 4.53). In terms of SDQ subscales, emotional problems were lower in the Gideru camp (β=-1.02, 95% CI=-1.80 to -0.24) and higher in the Sengele camp (β =1.30, 95% CI=0.36 to 2.23) compared to children from the Domanga camp. Similarly, when compared with children from the Domanga camp, those from the Gideru camp had lower levels of hyperactivity (β=-1.71, 95% CI=-2.48 to -0.94) and those from the Sengele camp had higher levels (β=1.73, 95% CI=0.80 to 2.65). Peer problems were lower in the Sengele (β=-0.71, 95% CI=-1.25 to -0.17) and the Ukumako camps (β=-0.80, 95% CI=-1.30 to -0.29) compared to the Domanga camp. There were no significant differences in conduct problems or prosocial behaviour between camps.

There was no evidence that living with fathers compared to living with mothers was associated with total SDQ scores.

There has been no research into paediatric psychiatric disorders in mixed-subsistence forager societies despite being a population of interest in investigating universal mechanisms of psychiatric disorders. Here we show that the prevalence of behavioural symptoms and psychiatric disorders in Hadza children—a group who live in an economic and social organisation of semi-monadic mixed-subsistence foraging is lower than in an agricultural society such as England.

Although we did not formally compare the prevalence of psychiatric disorders, we did not find evidence of any current disorder in male children and adolescents (except for one boy aged 4 whom we excluded from the main analysis), and most domains of behavioural symptoms of psychiatric disorders were lower in Hadza boys compared to girls. It is difficult to make direct comparisons of strengths and difficulties between Hadza children and English children. This is because the SDQ is scored according to subjective accounts of strengths and functional impairments in a range of domains. It is possible that specific behaviours which would be considered impairments in a Western society could be viewed as neutral or valuable in Hadza society e.g. motor overactivity or getting into fights.

The prevalence of ASD in Hadza children and adolescents appears to be higher than in the West and the prevalence of behavioural and emotional disorders is lower. We found four young people with ASD. Based on clinical characteristics and symptoms, one child was likely to have Rett’s syndrome, one was likely to have Down syndrome and one child meeting the criteria for ASD did not have any obvious chromosomal abnormalities, albeit with a possible facial dysmorphia. Two out of three children with ASD also met the diagnostic criteria for ADHD. This increased prevalence of ASD is of interest especially given the low prevalence of other disorders. Cerebral malaria, consanguineous marriages, widespread alcohol misuse in adults including pregnant women, and many women giving birth relatively late in life might explain some of these findings.

We have diagnosed only a handful of children or adolescents with emotional disorders. Some participants reported a range of specific fears in their children. These include fears of animals, most commonly elephants and leopards, fears of supernatural creatures, most commonly ancestors’ spirits and witches, fears of certain groups of people, most commonly Datoogas (a nearby pastoralist population) and fears of aspects of natural environment, most commonly storms and thunder. There was no evidence of significant distress or dysfunction associated with these fears except in the children with ASD.

No diagnoses of current depressive disorders were made. There was one participant who reported a brief episode of depressive features in two of her children. Their symptoms included sadness, loss of energy, loss of interest, irritability, negative thoughts and poor sleep. The episode appeared to be associated with the children’s mother leaving the camp to search for food and a temporary state of hunger.

We have found no evidence of self-harm, either by self-injury or by self-poisoning. Older women are familiar with the idea of decorating their skin by burning it intentionally creating skin patterns, but this behaviour is less common in older men. As well as considered beautiful, the patterns indicate strength and endurance. We have not observed these patterns in younger Hadza children. We observed self-injurious behaviour in the child with Rett’s syndrome and it was reported for the child with Down syndrome. The child with Rett’s syndrome hit her head with her hands repetitively when someone took away desirable objects from her.

We have found no evidence of eating disorders. Questions about eating disorders were often met with smiles and incredulity. Hadza spend considerable amount of time everyday hunting and gathering for food and the concept of a distorted body image appears entirely unfamiliar to them. Hadza appeared unexposed to the idea of being thin as a desirable characteristic. Hadza men display a preference for women with a lower profile waist-to-hip ratio [17]. Although being overweight is not an undesirable characteristic for a man, many Hadza would consider an overweight man unlikely to be a good hunter or a good tree climber [18].

Although we made no diagnoses of psychotic disorders, the concept of impaired reality-testing is familiar to Hadza. Across all camps throughout the study period we were aware of multiple discussions about a man who was likely experiencing a psychotic episode, possibly induced by smoking cannabis. Community members reported that the man had been shooting at people with poisoned arrows, injuring at least two. We were told he believed that they were trying to harm him, but there was no clear reason for this belief. He was reportedly ‘in hiding’ with two of his children (both under 10 years of age), using them as ‘lookouts’ and sending them to villages to obtain updates about him. Community members reported adult onset of this unusual behaviour following sustained daily cannabis use. This behaviour was described as bad “masalaka”.

Another example given to us was of a man who was engaging with adult-onset repetitive behaviours such as drawing circles around him. Whereas it is not possible to establish what this behaviour could have represented, he clearly had a significant functional impairment and was unable to continue his Hadza lifestyle. He had to move to a city and was begging for money there.

We have not found any evidence of child sexual abuse in the Hadza community. The concept of inappropriate touching of children’s genitals by adults appeared unfamiliar to our participants. Most people had no concept of child sexual abuse occurring in other cultures. One participant subsequently enquired if our questions were aiming at investigating the possibility of female genital mutilation (FGM) which is illegal in Tanzania but had been practiced by Hadzabe in the past. However, the idea of marrying very young girls is familiar. During the study period, an older man from a neighbouring tribe was reportedly arrested for agreeing to a marriage of his 14-year-old daughter who was still a school pupil with an older man. Our participants could not recall a similar problem with the Hadza people. The official age at which girls are supposed to get married is 18. However, as ages are approximate and marriages are not official, there is no way of being certain how old the girls are. We have seen one young woman aged about 18 according to her own estimate who had a 4-year-old child, so early marriages must occur at least sometimes in the Hadza community.

This is the only study to date which has investigated behavioural symptoms and the prevalence of psychiatric disorders in children in a mixed-subsistence foraging tribe. Comprehensive screening tools with cross-cultural validity were used to investigate a large range of behaviours and mental disorders. The comparator group was a large nationally representative community sample of a modern society. As the Hadza population is small, it was possible to interview a large percentage of the overall population of Hadza children existing today. This means that the prevalence of behavioural symptoms and psychiatric disorders in our sample population is likely to resemble the prevalence in the overall population of Hadza children.

This study has several limitations. As there has been little research into the mental health of mixed-subsistence foraging populations, the ICD-10 system of diagnostic classification has not been validated in our sample population. However from narrative descriptions of tribe members’ understanding of mental illness, they appeared to describe discrete constructs of mental illness which broadly map onto some ICD-10 constructs of mental disorders. Due to marked economic, social and cultural variation across mixed-subsistence forager groups globally, it is difficult to draw conclusions about the prevalence of childhood psychiatric disorders in this system generally based on studying one group in isolation.

Hadza concepts of age do not neatly map onto modern constructs, and written records of birth dates are sparse. The concept of ageing is marked by features of physical development (e.g. a child being able to wrap their right hand over their head and cover their left ear means they are old enough to attend school), and thus it was difficult to accurately gauge the overall numbers of Hadza children. This also meant it was difficult to know the exact age of some Hadza children, which could be a confounding factor in the sample selection and results.

The estimated population of Hadza children is much smaller than the sampling frame of MHCYP 2017. This makes direct comparisons of prevalence rates of mental disorders difficult as the Hadza prevalence rate is impacted far more by a small change in absolute numbers than in MHCYP 2017. Individual-level data for MHCYP 2017 was not available, which prevented direct comparisons of Hadza children with subgroups of interest in MHCYP 2017 e.g. children of very low socioeconomic status. Due to time and resource constraints, it was not possible to administer a DAWBA to all children who completed an SDQ, this could impact the estimates of prevalence of mental disorders.

Our findings partially support the universality of mechanisms causing some childhood psychiatric disorders: while the prevalence of ASD is higher than in Westernised societies, we did not find evidence of childhood depressive disorders or behavioural disorders, and eating disorders are completely unheard of. We postulate that the reasons behind the low prevalence of most psychiatric disorders in this economic system and social organisation are likely to be highly complex. This could be due to several factors including the extraordinary community support we observed that the affected young people receive, more active lifestyles, differences in gut microbiome [19], and differences in social cognition [15]. Community support and community cohesion is one of the strongest known predictors of good mental health in young people [20].

This is the first study investigating the prevalence of behavioural symptoms and mental disorders in the children of a mixed-subsistence foraging population. This is a cross-sectional study of prevalence of psychiatric symptoms and disorders, thus longitudinal study designs are warranted in order to acquire more accurate descriptions of mental health in Hadza children, and children in other mixed-subsistence forager groups globally. Further research is needed into the causes of disparities in the prevalence of mental disorders with established cohorts which could be observed over time in these population compared to children in Westernised societies. We anticipate that our findings can inform the direction of the treatment of psychiatric disorders in children and adolescents globally.

Population and study design

Two authors travelled to the region in northern Tanzania where Hadza people live during the dry season. One camp was identified as a starting position based on proximity to Arusha where the authors travelled from, and three further study sites were chosen according to opportunistic travel capabilities between camps. The four camps in the final sample were Domanga, Gideru, Sengele and Ukumako. No camp movements were observed during the study period. The sample size was determined by how many verbal administrations of established psychometric tests could be conducted in the available study time. On arrival to the camp, the researchers were introduced by the Swahili/Hadzane interpreter, and an explanation of the research was given. All children between the ages of approximately 3 and 17 years old residing in four Hadza camps were identified as the sample population. Each child’s mother or primary carer was also identified. All identified children and their mother/carers available for interviews between July-August 2021 were approached with an opportunistic sampling method and invited to participate. Informed consent was obtained orally from all participants. The process of obtaining consent and all assessments were video-recorded. One researcher administered the assessment via the interpreter, and the other researcher filmed the assessment. These roles alternated in each assessment. Participants were given tobacco, cooking salt, and material for clothes for their participation.

Socio-demographic factors

Socio-demographic data were provided by the mother/carer and included: age; family size; educational level; whether the mother/carer currently leads a predominantly hunter-gathering life; whether their children go to school and if so, to what type of school; which camp the child lives in; child’s physical disability; child’s alcohol use; child’s tobacco use; child’s drug use. We recorded the presence or absence of the participants’ family members in the camp. The presence of the child/young person’s father in camp was recorded if he currently lived in the same camp as the participating mother/carer (even if the father was no longer in a relationship with their mother).

Mental Health of Children and Young People in England 2017: Comparator group

The Mental Health of Children and Young People in England 2017 (MHCYP) survey is an English national cross-sectional survey involving a stratified multistage random probability sample of children and young people, and their parents and teachers (n = 18,029) 21. The full methodology is detailed elsewhere [22].

Sampling was taken from the National Health Service Patient Register as a nationally representative sampling frame. Children and young people were eligible if they were aged 2 to 19, lived in England, and were registered with a general practitioner. Participants were administered a variety of tests including the Strengths and Difficulties Questionnaire (SDQ) [23], and the Development and Well-Being Assessment (DAWBA) [24] to establish the prevalence of psychiatric disorders. The SDQ is the most commonly used validated cross-cultural behavioural screening tool for child and adolescent mental health globally. The DAWBA is a package of interviews, questionnaires and rating techniques which has been used in all English nationwide surveys of children and young people to establish diagnoses of psychiatric disorders. Outcomes were reported according to age groups 2–4, 5–10, 11–16, and 17–19. We chose to use the pooled results from the 5–10 and 11–16 groups as our comparator, as they most closely resemble the age group of the Hadza population. As the Hadza population was largely unaffected by the coronavirus pandemic, we chose to compare data from Hadza children and young people with pre-pandemic data from the MHCYP 2017.The MHCYP data for the SDQ and DAWBA outcomes are only available as summary data, and thus inferential statistics were not possible.

Measures of mental health and paediatric mental disorders

To establish the prevalence of positive and negative behavioural symptoms, the Swahili parent-report version of the SDQ was administered to all mothers/carers of the sample population. To establish the prevalence of paediatric mental disorders according to the International Classification of Diseases (ICD-10) [25], the Swahili version of the DAWBA was administered to mothers/carers of the sample population. All SDQs and DAWBAs were conducted by two authors (DO and EW) with a local interpreter fluent in both Swahili and Hadzane.

Statistical Analysis

Sociodemographic factors and psychiatric diagnoses were summarised as means and standard deviations, medians and interquartile ranges (IQR), and frequencies. SDQ scores were summarised as means and confidence intervals to allow comparison with SDQ data from the MHCYP 2017. Descriptive results are provided for both the overall Hadza sample (aged 3–17 years) and Hadza children aged 5–16 years to facilitate comparison with MHCYP 2017 data. Cross-sectional associations between sociodemographic factors (age, sex, camp, and which parent they live with) and total and individual domain SDQ scores in the overall sample (aged 3–17 years) were explored with the use of linear regression models.

Multiple imputation using chained equations was performed to deal with missing data on the SDQ. Multiple imputation was based on SDQ items for which there were no missing values [26].

All statistical analysis were performed using STATA 17.0 (Stata Corp LLP, College Station, TX).

Conflicts of interest

The authors declare no conflicts of interest.

Ethics

This study complies with all relevant ethical regulations. King’s College London’s Research Ethics Committee approval was obtained, REC reference number HR/DP-20/21-23691. We obtained informed consent from all participants, including informed consent from a parent/guardian for study participation by minors.

Data availability

The datasets generated during and/or analysed during the current study are available from the corresponding author upon reasonable request.

Acknowledgements

We thank Mariamu Anyawire for her interpreting services. We thank Emma Wilson and Jérémy Lemoine for scoring the SDQs. We thank Caitlin Aspinall for contributing to editing of the manuscript. We thank Quinton Deeley for his comments on the manuscript. Funding was provided by a grant to DO from King’s College London.

Author contributions

DO, EW and IO planned the study. DO and EW conducted the field work and performed the assessments. AR conducted the statistical analysis of the data and prepared the figures and tables. All authors were involved in the interpretation of the data. DO and GT drafted the manuscript. All authors discussed the work and made revisions to the manuscript.

Competing interests statement

The authors declare no competing interests

Data availability statement

The data that support the findings of this study are available from the corresponding author, DO, upon reasonable request.

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Table 1. Sample characteristics and results from the DAWBA assessment

	Overall sample aged 3-17y (N=107)	Subsample aged 5-16y (N=83)
	M±SD, N(%)	M±SD, N(%)
Camp
Domanga	49 (45.8)	37 (44.6)
Gideru	25 (23.4)	21 (25.3)
Sengele	15 (14.0)	11 (13.2)
Ukumako	18 (16.8)	14 (16.9)
Age	8.50±3.80 (n=140)	9.03±3.31 (n=113)
Female	57 (53.3)	44 (53.0)
Lives with mother	75 (70.1)	56 (67.5)
Lives with father	64 (59.8)	47 (56.6)
Education	31 (29.0)	28 (33.7)
Years of education	4.14±2.59 (n=29)	4.19±2.67 (n=26)
Physical disability	3 (2.8)	2 (2.4)
Psychological problems	3 (2.8)	3 (3.6)
Alcohol consumption	0 (0.0)	0 (0.0)
Tobacco use	6 (5.6)	5 (6.0)
Marijuana use	4 (3.7)	3 (3.6)
Psychiatric diagnosis
Autism spectrum disorder	4 (3.7)	3 (3.6)
ADHD	2 (1.9)	1 (1.2)
Social anxiety	1 (0.9)	1 (1.2)

Table 2. Means and 95% confidence intervals of Hadza children and of MHCYP 2017 survey

	Overall sample (N=140)		Aged 5-16y (N=113)		MHCYP 2017 Aged 5-16y (N=2588)
	M, 95% CI		M, 95% CI		M, 95% CI
Total difficulties	6.84, 6.12 to 7.57		7.14, 6.29 to 8.00		8.0, 7.7 to 8.4
Emotional problems	1.20, 0.93 to 1.48		1.26, 0.94 to 1.57		2.1, 2.0 to 2.2
Conduct problems	0.49, 0.32 to 0.66		0.57, 0.37 to 0.78		1.4, 1.3 to 1.5
Hyperactivity	2.39, 2.04 to 2.75		2.52, 2.11 to 2.93		3.1, 3.0 to 3.3
Peer problems	2.77, 2.59 to 2.94		2.79, 2.58 to 2.99		1.4, 1.3 to 1.5
Prosocial	9.43, 9.20 to 9.67		9.40, 9.13 to 9.68		8.7, 8.6 to 8.8
Boys*	(N=50)		(N=39)		(N=1239)
		M, 95% CI	M, 95% CI	M, 95% CI
Total difficulties		5.71, 4.84 to 6.58	5.81, 4.80 to 6.81	8.6, 8.1 to 9.1
Emotional problems		0.88, 0.49 to 1.27	0.85, 0.41 to 1.28	1.9, 1.8 to 2.1
Conduct problems		0.18, 0.06 to 0.30	0.21, 0.05 to 0.36	1.5, 1.4 to 1.7
Hyperactivity		1.70, 1.18 to 2.22	1.72, 1.10 to 2.33	3.6, 3.4 to 3.8
Peer problems		2.95, 2.70 to 3.19	3.04, 2.76 to 3.32	1.5, 1.4 to 1.7
Prosocial		9.94, 9.85 to 10.03	9.92, 9.81 to 10.04	8.4, 8.3 to 8.6
Girls*		(N=57)	(N=44)	(N=1349)
		M, 95% CI	M, 95% CI	M, 95% CI
Total difficulties		6.22, 4.91 to 7.53	6.54, 4.88 to 8.20	7.4, 7.1 to 7.8
Emotional problems		1.12, 0.59 to 1.65	1.34, 0.68 to 2.01	2.3, 2.1 to 2.4
Conduct problems		0.35, 0.05 to 0.66	0.44, 0.04 to 0.83	1.2, 1.1 to 1.3
Hyperactivity		1.89, 1.38 to 2.41	1.94, 1.30 to 2.57	2.7, 2.5 to 2.8
Peer problems		2.85, 2.56 to 3.13	2.83, 2.50 to 3.15	1.3, 1.2 to 1.4
Prosocial		9.28, 8.78 to 9.78	9.27, 8.64 to 9.90	9.0, 8.9 to 9.1
*Information about sex was gathered for 107 CYP from the overall sample and 83 from the subsample aged 5-16 years. SDQ data for this subsample are presented here.

Table 3. SDQ scores by Hadza camp (N=107)

	Domanga (N=49)	Gideru (N=25)	Sengele (N=15)	Ukumako (N=18)
	M±SD	M±SD	M±SD	M±SD
Total difficulties	6.69±5.10	3.52±1.23	8.99±2.87	4.94±2.34
Emotional problems	1.10±2.09	0.08±0.40	2.40±1.35	0.89±1.18
Conduct problems	0.43±1.21	0.00±0.00	0.41±0.73	0.11±0.32
Hyperactivity	2.03±1.95	0.32±0.56	3.76±1.74	1.61±1.24
Peer problems	3.13±0.98	3.12±1.05	2.42±0.62	2.33±0.77
Prosocial	9.27±2.00	9.84±0.55	9.73±0.60	10.0±0.00

No competing interests reported.

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The Prevalence of Behavioural Symptoms and Psychiatric Disorders in Hadza Children

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Mental Health of Children and Young People in England 2017: Comparator group

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