In the present study, we observed a very high prevalence of depressive symptoms among street youth, with more than four in ten street youth reporting CES-D score ≥22. The greatest number of depressive symptoms were observed among weekly heroin users, followed by weekly crystal methamphetamine users, then weekly cocaine/crack users, and finally, daily marijuana users. In adjusted analyses employing a conservative CES-D cutoff score of ≥22, weekly heroin users and weekly crystal methamphetamine users had significantly greater odds of having a score above this threshold when compared to daily marijuana users.
It has long been observed that mood disorders and youth risk behaviors including drug use tend to cluster [1
]. Data drawn from a nationally representative sample of US adolescents have shown, similarly, that rates of depression are lower among drug-abstaining youth [23
]. However, the causal nature of this association continues to be debated in the literature, even despite large-scale epidemiological studies of mainstream youth. Some have argued that substance use results in biological, psychological or social changes that predispose an individual to depression, and from a preventive standpoint, the logical point of intervention is to prevent substance use altogether [1
]. Others have proposed that drug use represents a form of “self-medication” for a pre-existing mood disorder [2
], and that attempts to reduce substance use should primarily target underlying depression. A third plausible mechanism is that substance use and mood disorders share some other common predisposition (e.g.
, childhood stressors such as trauma, abuse or neglect, or poor attachment to parents, among others).
Because our data are cross-sectional in nature and describe only associations, it remains unclear which of these explanations best explains the extremely high rates of comorbid depression and drug use exhibited by our sample of street youth. Regardless, these mechanisms are likely to be very different among street youth as compared to their mainstream peers, and merit further study to aid preventive efforts targeting this population. Street youth, for example, are much more likely to have experienced important preceding and concurrent stressors such as abuse, neglect, homelessness, poverty, poor relationships with parents, among others [25
], a fact that renders the interrelationship between substance use and depression even more complex.
Furthermore, why some drugs (i.e., heroin and crystal methamphetamine) are significantly more likely than others to be associated with excessively high depressive symptoms merits further research. In part, these findings may be related to the physiologic effects of certain drugs. For example, stimulants such as cocaine, crack and methamphetamine are clearly associated with euphoria during acute intoxication, whereas withdrawal and craving are associated with dysphoria. Similar mood changes can be seen with acute intoxication with and withdrawal from heroin. A variety of other individual- (e.g., biological and psychological) and meso-/macro-level (e.g., social and environmental) characteristics are likely to contribute to depression and should be carefully explored in future studies. Some basic trends were noted among various drug-using categories. Marijuana users tended to be younger than other users, and were less likely to have ever been jailed previously. They were also less likely to have recently overdosed; indeed, heroin users were by far the most likely to have recently overdosed. Cocaine/crack users were more likely to be of Aboriginal ancestry and to engage in heavier alcohol use than other users. It also is unclear why depressive symptoms among weekly cocaine/crack users were not significantly different from those among daily marijuana users in the present analysis, particularly given the profound dysphoria that can accompany craving. Cocaine/crack users in our sample tended to have recently presented for drug treatment more frequently than frequent marijuana users, which may have served a protective role with regard to depressive symptoms. Ultimately, our analyses controlled for these various sociodemographic and drug-related variables where appropriate, but these data serve to inform policymakers of the characteristics of different drug users and may help further stratify users for their risk of depression.
Multiple studies of adult drug users have examined whether an individual's comorbid depression impedes abstinence following drug treatment. A series of studies have supported the notion that the prognosis of depressed users following treatment is poorer than their non-depressed counterparts, including among opiate users [28
] and cocaine users [28
]. Other studies, particularly among alcohol-dependent adults, have not supported the notion that depression affects drug treatment success [31
]. Similarly, a range of studies of adult users have shown that successful drug treatment may result in a reduction in depressive symptoms, a finding found among opiate users [34
] and amphetamine users [35
]. Whether drug cessation itself results in an improvement in depressive symptoms or whether some other component of treatment (e.g.
, social support provided by fellow participants) is responsible requires further study [39
]. However, it is noteworthy that another study of young methamphetamine users showed that depressive symptoms significantly decreased following cessation or reduction of drug use regardless of whether they received treatment [20
This study has several limitations. In selecting our sample, we employed street-based outreach and snowball sampling, an approach that may lend itself to some degree of selection bias. However, it is worth noting that the characteristics of our sample are similar to those of other samples of street youth studied in western Canada [40
]. Moreover, although efforts are made to postpone the interviews of participants who are acutely intoxicated or withdrawing from a drug, it is possible that some such participants may have completed their interviews, and the validity of the CES-D has not been established in such individuals. Finally, as outlined earlier, it is important to bear in mind that our results draw on cross-sectional rather than longitudinal data. As such, it is inappropriate to draw conclusions regarding temporality and causality of the association between drug use and depression based on the findings of our study alone.
This study adds new knowledge to the literature on depression among street youth by delineating how the degree of depression varies by the principal drug of use. In particular, it highlights the substantially increased number of depressive symptoms among frequent heroin users and crystal methamphetamine users. Although street youth remain a population both understudied and underserved, they remain at great risk for premature death, and depression may be an important contributing factor by predisposing to suicide, overdose, and HIV-related risk behaviors such as injection drug use and unprotected sex [1
]. Our findings suggest that expanding mental health services to all
street youth is merited, particularly given the alarmingly high rates of substance abuse and numbers of depressive symptoms observed among our sample. However, in redoubling efforts improve such services, policymakers might heed the apparent vulnerability of heroin and crystal methamphetamine users to even greater levels of depressive symptoms than their other street-involved peers.