Depression and Alcohol Abuse: Dual Diagnosis and Comorbidity

Introduction to Dual Diagnosis

The comorbidity — or dual diagnosis — of mood disorders, particularly depression, and alcohol abuse or dependence has gained increasing attention in recent years due to the frequency with which the two conditions co-occur. Depression and alcohol use is a topic that sparks considerable discussion, as depressive symptoms can both precede and follow the onset of alcohol dependence (Sokya, Hollweg & Naber, 1996). This often leads to a "chicken or the egg" (Flensborg-Madsen, 2011) type of question: which came first — the abuse or dependence, or the depression? Whichever came first, evidence indicates that a causal relationship exists between the two disorders (Flensborg-Madsen, 2011).

Defining Alcohol Use Disorders and Depression

Alcohol abuse is defined as an alcohol use disorder characterized by sustained drinking despite negative consequences, as well as an inability to take responsibility for one's own actions, especially in relation to those consequences. Alcohol dependence, on the other hand, is characterized by a desire or craving for alcohol, possible physical dependence on alcohol, increasing tolerance to alcohol's effects, and an inability to control one's drinking habits (Petrakis, Gonzalez, Rosenheck & Krystal, 2002).

The DSM-IV-TR defines a major depressive episode as the presence of five or more of the following symptoms during the same two-week period, with at least one symptom being either depressed mood or loss of interest or pleasure:

1) Depressed mood most of the day, nearly every day; 2) markedly diminished interest or pleasure in all or most activities; 3) significant weight loss when not attempting to lose weight; 4) insomnia or hypersomnia almost every day; 5) psychomotor agitation or retardation nearly every day; 6) fatigue or low energy nearly every day; 7) feelings of worthlessness or excessive guilt nearly every day; 8) diminished ability to think or concentrate nearly every day; and 9) recurrent thoughts of death, including suicidal ideation with or without a specific plan (Mental Health Today, 2012). Major depressive disorder can be diagnosed following a single major depressive episode.

Causal Relationship Between the Two Disorders

Based on a meta-analysis conducted by Boden and Fergusson (2011), it was concluded that the presence of one disorder — either an alcohol use disorder or depression — doubles the risk of developing the second disorder. However, the authors hypothesized that the most plausible causal direction is one in which the alcohol use disorder increases the risk of depression, rather than the other way around.

The symptoms that may arise in a person who is both alcoholic and depressed are defined by the DSM-IV-TR as described above — including depressed mood, lack of interest or pleasure, insomnia or hypersomnia, thoughts of death, significant weight loss, and psychomotor agitation or retardation. Importantly, some of these symptoms may also be brought on by alcohol use itself — for example, insomnia and psychomotor agitation. Because alcohol is a central nervous system depressant, its effects may exacerbate certain depressive symptoms, which is why it is often difficult to determine which disorder preceded the other.