AD has principally been studied in clinical samples. Epidemiologi-cal data in adults are not available. The AD diagnosis was not in-cluded in the Epidemiologic Catchment Area Study and there are only a few studies in children and adolescents. Prevalence rates for AD range from 2.3% of walk in clinic patients who had no other Axis I or II disorders to 20% when comorbid axis I and II diagnoses were present. In a Pittsburgh sample, 16% of the children and ado-lescents younger than 18 years were diagnosed with AD (Fabrega et al., 1986). In adults, women predominated over men by approxi-mately 2 : 1. The sex ratio was more equal in children and adoles-cents, although there was still a slight excess of female patients.
Prevalence estimates of AD in other clinical populations have been characterized by considerable variability. In general hospital inpatient and psychiatric consultation populations, AD was diagnosed in 21.5 and 11.5%, respectively (Popkin et al., 1988; Snyder and Strain, 1990). Consultation–liaison data from seven university teaching hospitals in the USA, Canada and Australia revealed that AD was diagnosed in 125 patients (12.0%); as the sole diagnosis in 81 (7.8%); and comorbidly with other Axis I and II diagnoses in 44 (4.2%) (Strain et al., 1998). It had been considered as a “rule-out” diagnosis in an additional 110 (10.6%). AD with depressed mood, anxious mood, or mixed emotions were the most common subcategories used. AD was diagnosed comor-bidly most frequently with personality disorder and organic men-tal disorder. Sixty-seven (6.4%) were assigned a V code diagnosis only. Patients with AD compared with other diagnostic categories were referred significantly more often for problems of anxiety, coping and depression; had less past psychiatric illness; and were rated as functioning better – all consistent with the construct of AD as a maladaptation to a psychosocial stressor. Interventions employed for this general hospital inpatient cohort were similar to those for other Axis I and II diagnoses, in particular, the prescrip-tion of antidepressant medications. Patients with AD required a similar amount of clinical time and resident supervision.
Oxman and coworkers (1994) observed that 50.7% of elderly patients (aged 551 years) receiving elective surgery for coronary artery disease developed AD related to the stress of sur-gery. Thirty percent had symptomatic and functional impairment 6 months following surgery. It is reported that more than 25% of elderly patients examined 5 to 9 days following a cerebral vascular accident had symptoms that fulfilled the criteria for AD. Spiegel (1996) observed that half of all cancer patients have a psychiatric disorder, usually an AD with depression. Since patients treated for their mental states had longer survival time, treatment of depres-sion in cancer patients should be considered integral to their medi-cal treatment. AD is a frequently made diagnosis in patients with head and neck surgery (16.8%), patients with HIV dementia (73%) and cancer patients (27%). AD is seen in dermatology patients and suicide attempters examined in an emergency department. Other studies include diagnosis of AD in more than 60% of inpatients being treated for severe burns, 20% of patients in early stages of multiple sclerosis and 40% of poststroke patients.
There are two published epidemiological studies in popula-tions of children and adolescents that included AD. One determined the prevalence rate of AD was 7.6% if an upper limit of 70 on the Children’s Global Assessment Scale (CGAS) is applied. However, if an upper limit of 60 is imposed (corresponding to “moderate” impairment on the CGAS), the prevalence of AD dropped to 4.2%. This indicates that up to 40% of AD diagnosed patients have only mild impairment, more than for any other diagnosis.
The relationship between family functioning and AD was evaluated by administering the Family Assessment Devise (FAD) to families who had a member with one of seven men-tal disorders: schizophrenia, bipolar disorder, major depression, anxiety disorder, eating disorder, substance abuse and adjustment disorder (Friedmann et al., 1997). Regardless of which specific psychiatric diagnosis was present in the family member, having a family member in an acute phase of any of these psychiatric disorders – even a subthreshold diagnosis such as AD, was a risk factor for poor family functioning. AD in a family member was a significant family stressor.