We identified depression in patients with text strings on the problem list that bridged to depression diagnoses. Patients with one of these diagnoses or a prescription for an antidepressant medication dated earlier than January 1, 1996, were excluded from treatment analyses. We calculated incidence rates for depression as the number of new diagnoses divided by the number of eligible patients.
We classified psychopharmacologic agents as either antidepressants or other psychotropic medications. We subclassified antidepressants as (1) selective serotonin reuptake inhibitors (SSRIs); (2) tricyclic and tetracyclic agents (TTAs); or (3) other antidepressants. Other psychotropic medications were subclassified as (1) benzodiazepines; (2) other antianxiety agents; or (3) others, which included antipsychotic and antimania medications.
For new cases of depression, we defined a “definite follow-up” as another contact where a diagnosis of depression or another prescription for an antidepressant medication was recorded. Since physicians often address problems beyond those documented at each visit, we defined a “possible follow-up” as all definite depression follow-ups plus contacts for other diagnoses.
Initial analyses revealed that a large proportion of patients who received antidepressants in 1996 had never been diagnosed with depression. To explore this issue, we examined all diagnoses for these patients within 5 days of the date of the antidepressant prescription. We performed analyses for all eligible patients in PPRNet and for each practice. Results are reported using simple descriptive statistics. We used chi-square statistics for comparisons of nominal data.
Results
Demographic Information
Thirty-nine of the 68 PPRNet practices were eligible for the study. The 29 noneligible practices were excluded for the following reasons: enrollment in PPRNet after July 1, 1995 (21); specialty or urgent care practices (7); or did not reliably record diagnoses (1). Sixteen (41%) of the eligible practices were in rural environments; the remainder were in suburban or urban settings. The specialty distribution among the eligible practices included 32 family medicine (7 academic, 25 community), 6 general internal medicine, and 1 combined family medicine and internal medicine. A total of 389 physicians saw patients in the 39 practices during the study year.
There were 149,327 patients eligible for the study, 88,727 women (59.4%) and 60,272 men (40.4%). The gender was unknown for 328 (0.2%) patients. The age distribution was as follows: 54.7% aged 18 to 45 years; 26.0% aged 46 to 65 years; and 19.3 % aged 66 years or older. The median number of patients per practice was 2785 (range = 192 - 21,120). Socioeconomic information, such as occupation or insurance coverage, is not consistently maintained in the PPRNet database.
Diagnosis and Treatment of Depression
We excluded 18,186 (12.2%) of the 149,327 patients from this portion of the analysis. Among those excluded, 3231 (17.8%) had a previous diagnosis of depression, 7658 (42.1%) had previously received an antidepressant, and 7297 (40.1%) had been given a depression diagnosis and an antidepressant prescription before 1996. A greater number and proportion of women (13,329, 15.0%) than men (4852, 8.0%) were excluded.
A total of 2103 (1.6%) of the 131,141 patients without a documented history of depression or antidepressant prescription had a new diagnosis of depression in 1996 Table 1. There were 213 problem text strings in the electronic medical record that were bridged to depression for these 2103 patients. However, 72% were categorized as “depression,” and 6% were “depressive disorder.” Women were more likely than men to receive these diagnoses. Wide variation was found among the 39 practices in the incidence of depression (range = 0.4% - 4.0%).
Of the newly diagnosed patients, 1032 (49.1%) were started on antidepressants within 5 days of the initial visit for depression Table 1. Of those, 934 were given antidepressants alone, and 98 patients were also prescribed other psychotropic medications. Ninety-four newly diagnosed patients (4.5%) were prescribed only nonantidepressant psychotropic medication, and 977 (46.5%) patients not prescribed psychotropic medications within 5 days. Of the antidepressants prescribed within 5 days of depression diagnoses, 81% were SSRIs and 13% were TTAs. Of the other psychotropic medications prescribed, 73% were benzodiazepines and 14% were other antianxiety medications. Three hundred fifty-three (33.0%) of the 1071 patients diagnosed with depression who were not prescribed antidepressants within 5 days of their diagnoses received an antidepressant prescription by the end of 1996.
Among the 1032 patients given antidepressants, 69.9% had at least one definite follow-up appointment, and 90.5% had at least one least one definite or possible follow-up contact in the 6 months after their diagnosis. Among those with a follow-up, the mean number of contacts was 5.3.
Total Antidepressant Use
Overall, 9335 (6.3%) of the 149,327 patients received a prescription for an antidepressant in 1996 Table 2. Wide interpractice variability was present in the prescription of antidepressants (range = 1.9% - 13.6%). A total of 6443 diagnoses were made for these patients within 5 days of their antidepressant prescription. We present the distribution of these diagnoses in Table 3. One third of the patients (3045) who received antidepressants had a previous diagnosis of depression and had received antidepressants before 1996. Those patients were considered prevalent cases of depression and account for 2% of the total population. Four thousand twenty-two patients (more than 40% of the patients who received an antidepressant in 1996) never received a diagnosis of depression.