Panic Disorder: Comorbidity

Comorbidity

Lifetime comorbidity (i.e., the cooccurrence of two or more dis-orders at any point in a person’s life, regardless of whether or not they overlap) in panic disorder is common, with over 90% of community-dwelling and treatment seeking patients having had symptoms meeting diagnostic threshold for at least one other disorder (Robins et al., 1991). Comorbidity can pose consider-able challenge to treatment. The most common comorbid di-agnoses with panic disorder are other anxiety disorders, major depression, somatoform, pain-related, substance use and person-ality disorders.

Other Anxiety Disorders

The rates of lifetime comorbidity between panic disorder and other anxiety disorders, although variable across epidemiological studies, are high. The most common comorbid anxiety disorders are social phobia and generalized anxiety disorder (15–30%) fol-lowed by specific phobia (2–20%), obsessive compulsive disor-der (10%), and post traumatic stress disorder (2–10%) (American Psychiatric Association, 2000). To date, there are no studies that have reported comorbid panic disorder and acute stress disorder. The most parsimonious explanation of high comorbidity between panic disorder and the other anxiety disorders is that they share a common diathesis.

Major Depressive Disorder

Epidemiological studies indicate that major depressive disor-der occurs in up to 65% of patients with panic disorder at some point in their lives. In approximately two-thirds of these cases, the symptoms of depression develop along with, or secondary to, panic disorder. However, since depression precedes panic dis-order in the remaining third, depressive symptoms cooccurring with panic disorder cannot be considered simply as a demoralized response to paroxysms of anxiety. While the risk of developing secondary depression appears to be more closely associated with the severity of agoraphobia than with the severity or frequency of panic attacks, this may be a confound of misdiagnosing some behavioral manifestations of depression as agoraphobia. Panic disorder and depression do not appear to be identical disorders and their co-occurrence may be due to a shared diathesis or mu-tual exacerbation of symptoms.

Somatoform and Pain-related Disorders

Somatoform and pain-related disorders are frequently comorbid with panic disorder. For example, hypochondriasis has been di-agnosed in approximately 20% of panic disorder patients attend-ing general medical clinics and in almost 50% of those attend-ing anxiety disorders clinics. Acute and chronic musculoskeletal pain (i.e., pain that persists for six months or longer), respec-tively, are reported by approximately 85 and 40% of panic disor-der patients attending anxiety disorders clinics. Irritable bowel syndrome, a condition characterized persistent abdominal pain and defecation difficulties, cooccurs in 17 to 41% of treatment seeking panic disorder patients. Emerging evidence suggests that comorbidity between panic disorder and both somatoform and pain-related disorders may be best explained by a shared diathesis model.

Substance Use Disorders

Panic disorder can be precipitated by the use of psychotropic drugs and risk is higher with chronic use. Alcohol has been iden-tified as playing a precipitating, maintaining and aggravating role in panic disorder. The 6-month prevalence of alcohol abuse or dependence in panic disorder has been reported to be 40% in men and 13% in women. These rates are higher than those observed in people with other anxiety disorders and those with no anxiety disorder. Although alcohol problems have been reported to pre-cede panic disorder in a majority of cases, most reports indicate that alcohol problems develop secondary to panic disorder, often as a means of self-medication. Those having panic disorder withagoraphobia appear to be at greater risk for comorbid alcohol abuse or dependence than those without agoraphobia.

Personality Disorders

Lack of reliable assessment instruments for personality disorders as well as overlapping diagnostic criteria necessarily limit the degree of confidence in reports of comorbidity with panic disor-der. Notwithstanding, 40 to 50% of panic disorder patients have been reported to qualify for one or more personality disorders, a rate which exceeds that of 13% observed in community control samples. The most commonly reported cooccurring personal-ity disorders are avoidant, dependant, and histrionic personality disorders. These disorders do not cooccur uniquely with panic, also being common in patients with depression and other anxi-ety disorders, and they often persist despite remission of panic symptoms.