Treatment for opioid dependence is effective in improving a range of both individual and public health outcomes. One factor that may compromise therapeutic outcomes is comorbid depression or depressive symptoms. This thesis addresses a series of questions about the relationship between depression and opiate dependence treatments. In particular: is depression associated with dependence and risk taking in non-treatment populations; are any opioid treatments superior for opiate users with comoribid depression; and is antidepressant treatment effective for opiate users with depression.
Little is know about heroin users not in treatment. The first project examined the relationship between depression and drug use variables in a sample of non-treatment seeking heroin users. 70 heroin users who had never sought treatment were recruited and underwent a comprehensive interview. Depression symptoms were found to be related to dependence severity and social functioning, suggesting that heroin users with no treatment history may be more likely to seek treatment. Heroin users with depressive symptoms also reported treatments as more appealing and useful.
Naltrexone is an opiate antagonist used in the treatment of opioid dependence to facilitate rapid detoxification and to promote relapse prevention. Some reports suggest that naltrexone may cause depression or dysphoria. The second project examined the incidence of depressive symptoms and their prognostic significance within a randomised controlled trial of rapid opiate detoxification and naltrexone treatment for opioid dependence. 159 opiate users were randomised to receive either rapid opiate detoxification and naltrexone treatment or to receive methadone maintenance. Results suggest that in patients complying with treatment, naltrexone may lead to an improvement in depressive symptoms.
Buprenorphine is a partial opiate agonist with similar efficacy to methadone when used as a maintenance treatment. Some reports suggest that buprenorphine may have an antidepressant effect. Utilising participants from a larger randomised controlled trial, no antidepressant effect of buprenorphine compared to methadone was observed. Differential predictors of depressive symptoms at three months between those on methadone and buprenorphine suggest that buprenorphine may be impacting differently on symptoms, and suggest a need for larger sample sizes in future studies of this nature.
Antidepressant drugs are important treatment options for depression, yet research on their efficacy in opioid dependent patients is conflicting. 49 stable methadone maintenance patients with depressive symptoms were recruited to participate in a randomised, controlled trial of fluoxetine versus placebo. Depressive symptoms improved over time in all subjects with no group differences. Poly-drug use improved only in those who completed the trial. These results suggest that first-line use of fluoxetine to treat methadone maintenance patients with depressive symptoms may not be appropriate and that such patients may benefit from non-drug intervention.
In summary, results discussed within this thesis suggest that depression is not only important for treatment populations, but also for non-treatment samples, and that within such groups, depression may be associated with greater dependence and thus the greater need for treatment of the core drug-use disorder. Initiating any of the pharmacotherapeutic interventions is associated with a reduction in depressive symptoms. Thus the presence of depressive symptoms at treatment entry need not drive choice of treatment. Provision of good opioid dependence treatment will be sufficient for most patients - element of good treatment involve a client centred approach, use of adequate doses, and provision of psychosocial support.