Our sample was characterised by relatively young age, more recent HIV diagnosis, low level of virological or immunological failure and a distinct PS use pattern. These were consistent with other local reports (29, 38, 39) and contrasted with overseas cohorts that often consisted of men of older age with less favourable HIV outcomes (2, 40). Methamphetamine was the most commonly and frequently used substance, unlike the more prevalent use of cannabis or cocaine elsewhere. IDU rate was of the lower range compared to studies from the UK and Australia (2, 4). Methamphetamine users in our study had less frequent, less injection and shorter duration of methamphetamine use compared to overseas cohorts whose sexual orientation or HIV status were unspecified (10, 41, 42).
Consistent with literature, depressive disorders were the most common psychiatric diagnosis in our sample. The risk of lifetime depressive disorders in our cases (AOR 3.40, 95% CI 1.33–8.69, p = 0.01) was different from the lack of significant association of depression with methamphetamine use, slightly stronger than that with cocaine use and was comparable to that with drug abuse reported by Skeer, Mimiaga (40). Although comparison of their cross-sectional measures with our lifetime diagnosis is difficult, the difference observed could be related to their use of PHQ-9 which is less specific than the standard diagnosing tool and the inclusion of active users of other PS in the comparison group hence weakening their associations. It may also be explained by the more severe substance use in our sample: 52% of our cases fulfilled DSM-IV dependence criteria, whereas Skeer, Mimiaga (40) reported in their study that 55% of their substance users fulfilled the less restrictive abuse criteria using PHQ. The lack of description of methamphetamine use pattern by Forrest, Metsch (43) rendered comparisons to their results difficult.
The rate of lifetime psychotic disorders in our cases was comparable to other studies (10, 44) despite different assessment methods were used in samples with heavier and longer methamphetamine use. The proportion of lifetime methamphetamine-induced psychotic disorder among subjects with methamphetamine dependence (32%) resembled previous findings (10, 45, 46). The lack of schizophrenia was likely related to our small sample size with less frequent and shorter duration of methamphetamine use, based on the conversion rate reported by Niemi-Pynttari, Sund (47).
The lack of significant association of anxiety disorders with PS use observed in our study was similarly reported by Skeer et al. (2012). As homelessness, HIV symptoms and IDU predicted the anxiety level in PLHIV (48, 49), the absence of homelessness, few IDU and immunological failure in our cases may explain the low prevalence of anxiety disorder observed.
Corroborated with previous research (10, 11, 41), methamphetamine dependence and duration of methamphetamine use significantly predicted lifetime psychiatric disorders in our cases. The difference in rates of psychotic disorders as reported by McKetin, McLaren (10) could be related to different outcome measures. The infrequent and short duration of methamphetamine use in our non-dependent cases could also have inflated our odds ratio (Supplementary data Table S5). We showed that weekly use of methamphetamine for 2 years or more significantly predicted psychiatric disorders, concurred with previous findings on the positive relationship between frequency and duration of methamphetamine use and psychotic symptoms (10, 44).
A prominent finding from this study was the positive association between active PS use and psychiatric disorders appeared only for those with onset after HIV diagnosis. Our findings showed that weekly methamphetamine use of more than 2 years, methamphetamine use beyond chemsex and methamphetamine dependence predicted psychiatric disorders, and that all these factors correlated with a report of initiating or increasing methamphetamine use after HIV diagnosis. These observations suggested the diagnosis of HIV may have a critical impact in influencing the pattern of PS use and psychiatric diagnosis, although the characteristics of such relationships such as causality and temporality needs further evaluation.
This postulation concurred with earlier studies showing methamphetamine use was associated with the purpose to avoid unpleasant emotions in mixed-HIV status GBM (50) and to deal with negative emotions associated with HIV (51–53). Low mood was a major reason for PS use in local HIV-infected drug users, majority of whom were MSM (29). Our findings extended this knowledgebase and illustrated that using methamphetamine at non-sexual settings correlated with methamphetamine dependence and duration of HIV diagnosis and predicted psychiatric disorders. To avoid ongoing HIV transmissions, instead of using methamphetamine in chemsex which commonly took place over weekends, some cases reported using methamphetamine at other situations such as masturbation that could happen more frequently. This shift in the setting of methamphetamine use was probably unique in GBM, as chemsex with methamphetamine was much less common in the general population (54, 55).
The finding that the duration of HIV diagnosis predicated psychiatric diagnosis echoed previous results (56, 57) although direct comparison between the lifetime diagnosis and the point prevalence used in the other studies was difficult. The lack of significant association of psychiatric disorders with the stage of HIV infection echoed previous findings (21, 58, 59).
To our knowledge, this is the first study that examined PS use and its relationship with psychiatric disorders in HIV-infected GBM using a standard diagnostic tool. The incorporation of socio-demographic, HIV-related and substance-related factors in examining psychiatric epidemiology generated new insights into the possible inter-relationships among them. A case-control study design was more efficient than a prevalence survey and it minimised the sampling and surveillance bias when the cases and controls were compared. Multiple recruitment sources allowed sampling of subjects not engaged in HIV treatment during the study period, a situation more common among those with active PS use. The close collaborations with NGOs provided flexibility in scheduling the interviews at locations familiar and convenient to the subjects, facilitating recruitment of this hard-to-reach group. The inclusion of psychotic disorders filled a research gap that is relevant to the common use of methamphetamine in this population. The use of laboratory and clinical markers minimised recall bias.
This study had several limitations. Firstly, there was selection bias in non-randomised samples that limited the generalisability of our results. Our cases were largely comparable to the sample reported by Lee, Chan (29) regarding the proportion of viral suppression and living alone, although they were older with lower CD4 level. This could be explained by the discrepancy in case-mix where the hospital-based clinics were more likely providing care for patients with more severe disease, the minority of heterosexual subjects sampled and the lower CD4 observed with ageing. The lack of local data on PS use pattern in this population made assessment of the representativeness regarding these aspects difficult. Individuals with more severe PS use might not have joined the study, like when the substance use took priority. Sampling at the NGOs where free HIV testing services were provided might have resulted in sampling of subjects with relatively short duration of methamphetamine use. It is uncertain if our subjects joined the study for treatment leading to over-estimation of the prevalence of psychiatric disorders. Yet even if these exist, the comparisons between the cases and the controls should still be valid. Secondly, the results of this study could not indicate any causal relationships between the factors studied as our study was not powered to detect the differences in specific psychiatric diagnosis. Thirdly, there could be recall bias in substance use patterns, past psychiatric symptoms and ART adherence.