Differences in course and comorbidity of recurrent depression in primary care and psychiatric populations

INTRODUCTION Depression in psychiatric samples has been found to be more severe with greater functional impairment than depression in primary care settings [Schwenk et al., 1996]. However, depression appears to be recurrent in both treatment settings [Coyne et al., 1999]. In a recent study, we sought to compare the lifetime course of depression in these two treatment populations. We hypothesized that patients who sought treatment in a psychiatric setting would be more likely to exhibit a kindling pattern [Post et al., 1986], characterized by a reduction in time for recurrences of depression and a lower threshold of stressful events preceding later episodes. We also expected that patients from the psychiatric setting would have a more severe course overall with earlier onset, more recurrences, and more comorbidity than primary care patients. Patients with recurrent major depression (at least three total episodes) in a primary medical care sample (n1⁄4 38) were compared to patients with recurrent major depression in an outpatient psychiatry sample (n1⁄4 13) with respect to the timing of recurrences, the nature of stressful life events that preceded episodes, and Axis I comorbidity. Patients from the psychiatry sample were consecutive admissions to a community mental health clinic. Patients in the primary care sample were recruited from their physician’s waiting room. All participants were administered the Structured Clinical Interview for DSM-IV, Research Version (SCID) [First et al., 1997] to diagnose current and past mood disorders and other major Axis I disorders. The Structured Interview Guide for the Hamilton Depression Rating Scale [Williams, 1988] was used to assess depression severity. The SCID was modified to include additional questions regarding lifetime course of depression and stressful life events in the 6 months prior to episodes. Stressful life events were rated by committee for long-term threat, level of interpersonal versus intrapersonal involvement, and the role of the individual in causing the event, using Brown and Harris Life Events and Difficulties Schedule [Brown and Harris, 1978]. Both groups showed a reduction in time to later episode recurrences, consistent with Post’s kindling model [Post et al., 1986]. Contrary to the kindling model, neither group showed a decline in the presence or stressfulness of events preceding later depressive episodes. The groups did not differ in the number or nature of life events prior to the first episode of depression. However, the psychiatry group reported more stressful events preceding onset of the most recent episode. These events were more likely to be interpersonal stressful events and ‘‘dependent’’ events (events that the patient likely played a role in creating) than those that preceded recent episodes in the primary care group. This pattern of recurrence is consistent with the stress generation model [Hammen, 1991]. The psychiatry group had more symptoms of depression, more psychosocial problems, more dependent life events in the past year, lower general functioning, and was more likely to have been hospitalized for their depression than the primary care group. The psychiatry group also reported higher rates of comorbid disorders, particularly PTSD (lifetime rate1⁄4 66.7% vs. 29.3%) and dysthymia (lifetime rate1⁄4 75% vs. 24.2%). These disorders were more likely to be present during and between episodes of major depression in the psychiatric treatment group. There were also differences in the course of depressive episodes between treatment settings that suggested greater severity in the psychiatry group. In the psychiatry group, the most recent onset occurred after a significantly shorter remission period than found in the primary care group. In addition, the most recent episode was significantly longer, with a mean of over 2 years duration. The groups did not differ on age of onset, length of first episode, or overall number of episodes. These findings support previous research that has found depression in psychiatric treatment facilities to be more severe than depression in primary care settings [Schwenk et al., 1996]. Although groups were matched on the number of previous episodes, the psychiatry group had more psychiatric comorbidity, increased length of episodes over time with shorter periods of remission between episodes, and more interpersonal stressful events that the patients had a role in creating. In contrast, the patients in primary care were relatively free of comorbid disorders and had full remissions between episodes. Events prior to episode onsets were more likely to be related to circumstances beyond their control. Like the psychiatry patients, time to remission between episodes was DEPRESSION AND ANXIETY 20:153–154 (2004)