Comorbidity Patterns: Other Clinical Psychiatric Disorders

Comorbidity Patterns: Other Clinical Psychiatric Disorders

The presence of a comorbid psychiatric disorder may alter the course of major mood disorder in a dramatic fashion and is iden-tified as a primary risk factor for poor treatment response. More than 40% of patients with MDD have additional symptoms that meet criteria during their lifetime for one or more additional psy-chiatric disorders. In a sample, assessing both pure and comorbid MDD based upon findings from the NCS, the current prevalence of major depression was 4.9% (Blazer et al., 1994). Of the sam-ple with current MDD, 56.3% also had another psychiatric disor-der. Among respondents to the NCS-R, the 12 month prevalence of disorders were considered to be serious in 22%, moderate in 37.3% and mild in 40.4%. Twenty–two percent of those with dis-orders carried two diagnoses, and 23% carried three more diag-noses. The most common comorbid conditions were with major depression and included:

·        bipolar disorder (major depression with either hypomania or mania;

·        double depression (major depression with dysthymia);

·        anxious depression (major depression with generalized anxi-ety disorder

Alcohol/Drug Dependence

Results of family and twin studies in a population-based female sample are consistent with a modest correlation of the liability between alcohol dependence and MDD (Kendler et al., 1993). It is common for individuals with alcohol dependence to evidence signs of depression or MDD, but alcoholism is not thought to be a common consequence of mood disorder. Between 10 and 30% of patients with alcoholism manifest depression (Petty, 1992), whereas alcoholism is thought to occur in under 5% of depressed patients (Depression Guideline Panel, 1993).

Depressed women are more likely to self-medicate their mood disorder with alcohol than are depressed men. The effect of comorbid alcoholism on the course of major mood disorder is unclear. Some evidence suggests that remission of depression occurs within the first month of sobriety. The effect of comor-bid depression requires further attention in relation to the course of drug dependence. Drug dependence is often associated with major mood disorder and the presence of associated comorbid personality disorder.

Anxiety Disorders

The cooccurrence of symptoms of anxiety and depression is very common. Kendler et al. (1986) found very high genetic correla-tions between MDD and generalized anxiety disorder in con-trast to a modest overlap between phobic disorders and MDD. Anxiety symptoms commonly appear in depressive syndromes and MDD is frequently comorbid with anxiety disorders. From a longitudinal perspective, either symptom constellation can be a precursor to the development of the other disorder. The com-bination of anxiety and depression predicts greater severity and impairment than the presence of each syndrome in isolation. The association of severe panic and MDD is one of the predic-tors of suicidal risk. The clinician is advised to assess for symp-toms of each disorder and to obtain a thorough family history. Patients with anxiety disorders often experience prior episodes of MDD or have relatives who suffer from mood disorder.

Ten to 20% of outpatients with MDD evidence comorbid panic disorder while 30 to 40% of depressed outpatients have had symptoms that met criteria for generalized anxiety disorder dur-ing the course of the mood disorder. In both cases, the anxiety disorder has preceded the major mood disorder about 50% of the time. An increased incidence of MDD is noted in patients with anxiety disorders who are followed over time.

The clinician is advised to evaluate three factors in order to determine treatment approaches when MDD cooccurs with panic disorder or social phobia: 1) the patient’s family history; 2) the constellation of symptoms that were first evident in the current episode; and 3) the symptoms that cause the patient the most distress.

Recovery is less likely and symptomatology more severe in patients with comorbid MDD and panic disorder than in cases with a single diagnosis. Lifetime suicide rate is twice as high for patients with comorbid panic disorder and MDD than in panic disorder alone. It is imperative to assess for the presence of mood disorder and suicidality in patients who present with symptoms of anxiety.

Obsessive–Compulsive Disorder

The occurrence of symptoms of depression is very common in patients with obsessive–compulsive disorder (OCD), although full symptom criteria may not be reached to warrant a formal diagnosis of MDD. Ten to 30% of patients with OCD have mood symptoms that meet full criteria for MDD. The relationship be-tween OCD and schizophrenia is less clear. Patients with OCD are at increased risk to develop MDD but not schizophrenia. It is important to distinguish between obsessive–compulsive person-ality features which can accompany and are exacerbated during an episode of depression and OCD itself. Symptoms of depres-sion often diminish with successful initial treatment of OCD, since biological treatments typically involve use of selective serotonergic antidepressant medications such as clomipramine, fluoxetine, or fluvoxamine.