Data source and study design
Young Minds Matter (YMM): The Second Australian Child and Adolescent Survey of Mental Health and Wellbeing, conducted by the University of Western Australia (UWA) through the Telethon Kids Institute in collaboration with Roy Morgan Research and the Australian Government Department of Health during 2013–2014, was used to analyze cross-sectional data [24, 25]. Ethical approval has been obtained from the Human Research Ethics Committee of the University of Southern Queensland to conduct this research.
YMM used a multi-stage, area-based random sample technique that was representative of Australian households with children and adolescents aged 4–17 years. If the household had more than one qualified child, the sample included a single child at random. In total, 6310 parents of children and adolescents aged 4–17 years (55 percent of eligible households) voluntarily participated in the survey through a face-to-face interview using a structured questionnaire, and 2967 adolescents aged 11–17 years (89 percent of eligible youth) privately completed computer-based self-reported questionnaires to provide information on risk behaviors (e.g., suicidality, self-harm, substance use, bullying) and service use. The survey does not include the most rural places, homeless teenagers, adolescents in any type of institutional care, or homes where interviews could not be performed in English. The survey details and methodology used in the survey will be found in Hafekost et al. (2016) [25].
Measurements
Mental disorders
To maintain consistency with the first child and adolescent national survey and ensure maximum comparability among prevalence estimates, the DISC-IV scale was used [26]. DISC-IV diagnostic criteria are referred to in the Diagnostic and Statistical Manual of Mental Disorder (DSM-IV) formulated by the American-psychiatric association [26]. Worldwide DISC-IV remained the best tool for measuring the 12-month incidence of mental disorders in 2013. Primary carers completed the DISK-IV modules. Mental disorders included major depressive disorder, attention deficit hyperactivity disorder (ADHD), conduct disorder, and four types of anxiety disorders—social phobia, separation anxiety disorder, generalized anxiety disorder, and obsessive-compulsive disorder [27].
In this study, only parental data were used to create a binary variable to detect the presence of any mental disorder, as it only provided diagnostic information about each type of mental disorder in children and adolescents. Here we consider a variable ‘mental disorder’ in our analysis: whether the adolescent has had any of the following types of mental disorder- major depressive disorder, ADHD, conduct disorder, or anxiety disorders which includes social phobia, separation anxiety disorder, generalized anxiety disorder, and obsessive-compulsive disorder in the past 12 months. Responses included ‘Yes’ (if a child has at least one of these issues, the code is 1.) or ‘No’ (coded as 0 if otherwise).
Socio-demographic factors
In this study to identify different classes, our main variables of interest were socio-demographic factors of the adolescents and their corresponding households. Depending on income, regional status, employment, family history, and other variables, every country, and its people are categorized into numerous social classes or levels. While class distinctions are not completely evident or defined by any formal organization, they do exist in terms of how people live, conduct themselves, and spend money [21]. There are five main social classes in Australia (Figure 1) [21]. The following Figure 1 represents the five social classes of Australia with the mean characteristics of the different classes.
Each class is defined by its members' possession of economic, social, and cultural capital. There are also significant differences in the average ages, education, and occupational status of the members in each class. There is evidence of intergenerational mobility in occupational prestige across all groups, but particularly in the working and middle classes. This is most obvious in the two middle classes (mobile middle class and established middle class), where members' prestige scores are more than their parents' [21].
For this study, socio-demographic variables were represented by age (11-14 years vs. 15-17 years), Sex (male vs. female), income (less than $52000 as low, $52000–$129999 as medium, and more than $130000 as high), regions (metropolitan vs. non-metropolitan), primary carer education (bachelor, diploma, and year-12/below), primary carer occupation (employed vs unemployed), index of relative socio-economic advantage and disadvantage (IRSAD) quintile [lowest (most disadvantaged), second, third, fourth and highest (most advantaged)] of the parents, family blending (intact family vs other families) and both parents living status in the household, that is whether both parents live in the household or not (yes vs no). The last two variables indicate the family functioning of a household. In 2015, a study found that adolescents from non-intact households had a lower perception of family functioning, father’s and mother’s behavioral control, paternal psychological control, and parent-child relational traits than adolescents from intact households [28]. All of these socio-demographic variables were taken from three different levels. Figure 2 represents the framework for selecting these variables to determine the significant number of classes by using latent class analysis.
Study participants and data analysis
To determine the appropriate number of classes and to examine their probable associations with adolescent mental disorders data were taken from parent data on the DISC-IV. Age is an important factor in the mental health of children and adolescents, and children and adolescents aged more than 11 have a higher risk of mental health disorders [22]. A study by the Telethon Kids Institute found that children and adolescents belonging to the age group 12-17 years are almost three times more likely than the age group 4-11 years to experience a severe mental disorder [29]. Taking these into account, in our study, the sample is restricted to children and adolescents aged 11–17 years. In parent data, there are 6310 parents/carers involved with children aged 4–17 years. Since our study sample was restricted to adolescents 11–17 years and all the ‘don’t know’ responses were omitted therefore study participants were 3152 parents/carers.
Descriptive analysis
Descriptive analyses were carried out taking into account the variables that were used to find the latent classes. All variables used in this analysis are categorical. Proportions for each of the categorical variables are calculated using R. Bivariate analyses are conducted to examine the distribution and association of the socio-demographic characteristics with the mental health of the adolescents. Chi-square tests of significance are used to describe and compare the sample characteristics of adolescents with mental disorders.
Latent Class Analysis (LCA)
The LCA is a cluster analysis method that uses a probability model [30–32]. LCA, like all cluster analysis methods, finds homogeneous clusters of data from varied demographic and socioeconomic data by maximizing similarity within the cluster while minimizing similarity across cluster elements. LCA assumes the data is from a mixed model with several probability distributions[33]. It presumes that the data is divided into mutually exclusive homogeneous subgroups by a latent variable. LCA is said to have numerous distinct advantages over traditional cluster analysis approaches [31, 34]. Different statistical criteria are available in the LCA output, which can be used to identify the most appropriate number of clusters; and different types of variables (for instance, counts, continuous, categorical, nominal) can be used in LCA directly without any further standardization process [33].
In this study, using R (version 4.1.3) a latent class analysis was performed to identify and describe the classes associated with adolescents’ mental health. To determine the exact number of latent classes, an empirical approach was used [18]. Starting from a two-class model, the analysis was carried out several times consecutively, increasing the number of subgroups by turn and replicating each of the models 5 to 10 times for greater precision. Then, statistical model adjustment indices, such as the Bayesian information criterion (BIC), the Akaike information criterion (AIC) [35], the Likelihood ratio/deviance statistic [G^2], and Chi-square goodness of fit were used to identify the final number of classes. Indeed, the selected classes had to have enough observations to provide a representative class of a population [22]. In practice, subgroups with a size of less than 5% were not retained, as in similar studies [18]. The clusters were named in a way that best represented the most notable discoveries in the data. While naming the clusters made it easier to communicate them to the audiences [36], it is difficult to capture the level of difference across clusters with labels, according to the argument. The best potential name for each cluster's identifying traits was determined. The clusters were not meant to be displayed in a linear fashion.
Bivariate analyses and binary logistic regression
After determining the necessary number of latent classes, a series of cross-tabulations and bivariate analyses (using Chi-square tests) were used to investigate the distribution of and relationships between adolescents’ mental disorders. Two binary logistic regression models were fitted to observe the association between class membership and the mental health status of children and adolescents. The first model is considered without controlling any covariate and thus gives an unadjusted effect and the second model is based on considering the controlling variables; ‘household size’, ‘household type’, ‘inability to pay gas, electricity, or telephone bills on time’, ‘could not pay the mortgage or rent on time’, ‘adults/children have gone without meals’, and ‘households receive a carer benefit or pension in relation to child’ and this gives adjusted effects.