Opioid dependence is a complicated disorder, in which multiple factors interact to influence initiation of use, repeated use, addiction, and relapse (
1). Relapse rate after opioid detoxification ranges from 72% to 88% after 12 to 36 months, despite multidisciplinary endeavors, although a 6-month controlled study showed lower relapse rate (32% to 70%) (
1,
2).
Opioids induce long-lasting alterations in the nervous system. Some of these changes are responsible for the physical dependence that causes an aversive withdrawal syndrome when the central nervous system opioid levels decline. Other drug-induced changes that may persist for some time after withdrawal include a hyper responsiveness to stress, a reduced response for ordinary pleasurable events (hypophoria) and a persistent memory for conditions under which opioids were used. It is not yet clear whether these changes should be considered part of protracted withdrawal syndrome or whether they represent a distinct phenomenon (
1). Chronic opioid addiction may lead to opposing opioid receptor responses in the Nucleus Accumbens during withdrawal, which may produce dysregulation in brain stress hormones (
3). Persistent alterations in stress hormone systems, and receptor and/or neurotransmitter activity may represent a compensatory mechanism, involving neuro-adaptations aimed at restoring homoeostatic function in response to the presence of the drug. As such, these changes could contribute significantly to negative emotional states of acute drug withdrawal, as well as enhanced sensitivity to stressful stimuli, both of which could result in greater vulnerability to relapse during abstinence in humans (
3-
5).
Mood disorders, including bipolar disorders and depression, are amongst the most common psychiatric comorbidities in patients with substance use disorders; a portion of high rates of comorbid mood disorders and substance use disorders may be due to confounding of mood disorders and transient symptoms related to acute abuse and withdrawal. Chronic use of drugs, such as central nervous system depressants may lead to depressive symptoms while withdrawal from some drugs like benzodiazepines could lead to agitation and anxiety. Thus, before making a definitive diagnosis, it is best to wait until the patient has had a reasonable period of abstinence (
6). A study found a 30% to 50% decrease in depression rating score from day one of abstinence to the end of the second week (
7). Furthermore, the pathological effects of substance use disorder or mood disorder may increase risk of the other, for instance mood disorders may motivate individuals to resort to drugs and alcohol to cope with their negative affective states (
6). Negative emotional states, such as anger, anxiety, depression, frustration, and boredom are associated with the highest rate of relapse (
8).
Depression could be a significant risk factor for relapse as it may lead to self medication. Furthermore, major depressive disorder may become a conditional cue for drug use during abstinence (
9).