The principal finding of this study is that depressed patients of practices randomized to the PROSPECT intervention had a higher likelihood to receive antidepressant treatment, a greater decline in suicidal ideation, lower depressive symptomatology, and a higher rate of response over 24 months than usual care patients. At any assessment point, 84.9–89% of intervention patients received antidepressants and/or psychotherapy while only 49–59% of usual care patients were treated for depression. The intervention was most effective in reducing suicidal ideation among patients with major depression. The decline was sharpest in the first 4 months and remained low up to 24 months. Similarly, severity of depression remained lower in intervention than usual care patients throughout the 24 months. Among patients with major depression, a greater number achieved remission in the intervention than the usual care group at 4, 8, and 24 months. The intervention had no advantages among patients with minor depression.
To our knowledge, this is the first study of 24-month depression care management focusing on suicidal ideation and depressive psychopathology in older primary care patients. Its findings are consistent with observations in mixed aged 18
primary care patients, including an intervention of 24-months duration 19
. In geriatric patients, the Improving Mood-Promoting Access to Collaborative Treatment (IMPACT) Study provided access up to 12 months to a depression care manager 20
. Primary care patients receiving the IMPACT intervention were more likely to receive antidepressant treatment than usual care patients and had better depression outcomes. The advantage over usual care was retained 12 months after the end of the intervention, although there was a decline of response and remission rates from 12 to 24 months 21
. In contrast, with continuing depression care management the response and remission rates in the intervention arm of the PROSPECT Study remained high or increased.
In most subjects, suicidal ideation was passive as often is the case in depressed primary care patients 22
. Even passive suicidal ideation requires attention. Depressed elders with passive suicidal ideation are more likely to have history of suicide attempts, higher scores of hopelessness 23
, slower treatment response, and lower rates of response than non-suicidal elders with major depression 24
. Passive suicidal ideation has a stronger association with medical comorbidity and service utilization than active suicidal ideation or no suicidal ideation 5
. Finally, 35% of patients with suicidal ideation change ideator status during the index episode; passive ideators become active or the reverse 23
. Change over time in passive suicidal ideation requires further research to identify treatment responsive and treatment resistant components that may further focus suicide prevention interventions for depressed older primary care patients.
There was one suicide and one suicide attempt in the intervention group, and three suicide attempts in the usual care group. These numbers do not allow statistical study of the relationship of suicidal ideation to suicide or attempts, but underscore the challenge of reducing the risk of suicide in primary care settings. The relationship of reduction in the rate of suicidal ideation, and especially passive or death ideation, to suicide remains to be determined.
Over 24 months, 49.7% of depressed intervention patients achieved remission (HDRS<7). Remission, defined as an almost asymptomatic state, is the optimal outcome because it is associated with low relapse rate and high function 25
. Randomized acute antidepressant trials show that 30–40% of patients achieve remission 26
. A controlled maintenance treatment trial showed that 65% of elderly patients with major depression remained in remission over 24 months while treated with paroxetine and monthly psychotherapy 27
. The remission rate of the PROSPECT intervention was somewhat lower than this figure. Nonetheless, demonstrating that a care management intervention can maintain almost half of depressed primary care patients in remission is evidence of a meaningful level of effectiveness.
While antidepressant prescriptions have been rising, many depressed primary care patients receive no antidepressant treatment 19
. Poor treatment adherence further compromises their care 28
. In this study, more than 84% of intervention patients received antidepressants or psychotherapy throughout the study, while only 49–59% of usual care patients received any antidepressant treatment.
Depression almost doubles the risk for death in community samples 29
. Patients of PROSPECT intervention practices with major depression had lower mortality than those in usual care practices (adjusted hazard ratio: 0.55, 95% CI: 0.36–0.84) over a 52.8 month median follow-up 17
, but there were no differences in mortality among patients with minor depression. This observation is consistent with reduced all-cause mortality reported in patients receiving antidepressants over 40 months in the Enhancing Recovery in Coronary Heart Disease Patients (ENRICHD) study 30
The benefits of the PROSPECT intervention on suicidal ideation and on depression were limited to patients with major depression. Patients with minor depression had overall favorable outcomes regardless of treatment assignment. At 24 months, only 6.2% of usual care patients had any suicidal ideation and 60.6% had achieved remission of minor depression. Given limited resources, patients with major depression should be the target of a care management intervention.
Limitations of the study include the use of SSI as the sole method for ascertaining suicidal ideation, the lack of information on discrete medical problems of participants, and on specific antidepressant treatments received by each group. Randomization at the practice level compromised the ability to blind raters. Covering the cost of citalopram and IPT limits study of cost as a barrier to treatment. Finally, attrition was relatively high, perhaps because the study enrolled a probability sample consisting of subjects less interested in study participation than help-seeking patients. Nonetheless, probability sampling permits safer generalization of findings. Moreover, the baseline clinical characteristics of those assessed at 24 months were similar to those of the sample initially entered. Finally, taking drop-out into consideration did not influence differences between treatment groups significantly. Another limitation is that suicidal ideation was assessed at single points in time although suicide thoughts wax and wane.
Strengths of this study include its random sampling and a sensitive screening approach designed to identify most patients with depression. These procedures allow generalization of findings to whole practices. Furthermore, the practices were heterogeneous and consisted of small, large, inner city, rural, academic, and privately owned practices. Finally, patients with suicidal ideation, cognitive impairment, and medical burden were included in the sample. Therefore, these findings may be relevant to real-world practices.
Primary care is a strategic point from which to fight suicidality and depression since most elderly patients suffering from these syndromes are treated by primary care physicians. Sustained collaborative care maintains high utilization of antidepressant treatment, reduces suicidal ideation, and increases response and remission rates of major depression over a period of two years. Rising response and remission rates between the 18th and the 24th month underscore the value of long term care. These observations suggest that sustained collaborative care increases both depression-free days and perhaps longevity.