Major depressive disorder (MDD) has historically been perceived as an episodic disorder . In the early 20th century, Kraepelin differentiated between "dementia praecox" (now known as schizophrenia ), which he considered chronic and progressive, and "(manic) depression" , which he described as episodic. This view has dominated our understanding of depression ever since.
Consistently, longitudinal observational research over the past century suggests that most MDD patients eventually recover from their index episode after relatively short follow-up assessments (e.g., 2 years) and suggests that ultimately only a A limited proportion follows a chronic course. This is further highlighted by the fact that most intervention trial research has strict treatment delivery and has focused on short- term remission of an episode.
Furthermore, randomized controlled trials generally include a subset of less severe patients who have, for example, a shorter duration of illness and lower rates of anxious and atypical symptoms. Therefore, the results of their course may not be representative and may be more positive than in "real world" patients , which has given rise to the idea that most patients recover over a period of time. relatively short and that only a minority has a chronic course.
Although the clinical course of MDD has been an extensive topic of debate, research results have generally led to an optimistic view. Furthermore, this has translated into correspondingly optimistic communication with patients and clinical management that aims for relatively short, episode-oriented treatments.
Although MDD may be limited to a single episode in some patients, Judd et al. have shown that most patients move in and out of more or less severe levels of symptoms over time. This suggests that, given a longer time frame, the prognosis is less favorable and that studies with a short follow-up time or relatively few evaluations will tend to underestimate the prognosis of MDD.
| Background |
Major depressive disorder (MDD) is often managed as an isolated, episodic disorder , resulting in an optimistic view about its prognosis. Here, we test the idea that the prognosis of MDD changes if we vary the perspective in terms of (1) a longer time frame and (2) a broader diagnostic conceptualization that includes dysthymia, (hypo)mania, and anxiety disorders such as relevant results.
| Methods |
Patients with current MDD at baseline (n = 903) and available follow-up assessments at 2, 4, and/or 6 years were selected from the Netherlands Depression and Anxiety Study, a psychiatric cohort study.
By combining DSM-IV-based psychiatric diagnoses and life-chart data, patients’ trajectories were classified into four course trajectories describing the course at three time points (2-, 4-, and 6-year follow-up). ):
- Recovered : no diagnosis at 2 years of follow-up or later;
- Recurrent, without chronic episodes : one or more diagnoses after onset, but never a chronic episode;
- Recurrent, with chronic episodes : one or more diagnoses after onset and at least one chronic episode, but not at all follow-up evaluations;
- Constantly chronic : A diagnosis is constantly present, a chronic episode at each follow-up evaluation.
A chronic episode was defined as having a current diagnosis at follow-up evaluation and ongoing symptoms for 2 years. Proportions of the course trajectories were provided from a short and limited perspective (2-year follow-up, considering only MDD diagnosis) to a long and broad perspective (6-year follow-up, including MDD, dysthymia, (hypo)mania and anxiety diagnoses).
| Results |
With the short and narrow perspective, the recovery rate was 58% and 21% had a chronic episode. However, in the long term, the recovery rate dropped to 17%, while 55% of patients experienced chronic episodes.
| Discussion |
This study tested the idea that the clinical course of patients with MDD may be underestimated when using a narrow perspective regarding the time frame or conceptualization of the diagnosis.
Consideration of long and rigorous follow-up in a large cohort of patients with MDD reveals that we may need to reconsider our conceptualization of MDD. Inclusion of symptoms from closely related disorders, such as (hypo)mania and anxiety symptoms, shows that the majority of patients have a chronic, disabling depressive disorder .
Conceptualizing MDD as a narrowly defined, episodic disorder may underestimate both the prognosis for most of our patients and, consequently, the type of appropriate care.
With a short and narrow perspective (2-year follow-up and MDD only), 58% of patients appeared recovered and only a minority (21%) had a chronic episode. With a long and broad perspective (6 years of follow-up, including affective and anxiety disorders), the recovery rate decreased to 17% and the proportion of patients with chronic episodes increased to 55%. The impact on daily functioning was found to parallel the severity of the course trajectory.
The current findings suggest that we may need to rethink the conceptualization of depression from an episodic, isolated disorder to a recurrent and often chronic disorder with high levels of comorbidity.
Several studies on the prospective long-term course of depression in the general population and primary care describe high rates of stable recovery from depressive symptoms (35-60%). However, the current study found that recovery rates were considerably lower when relevant comorbidity is included. Consequently, this suggests that approaching depression as a recurrent, but mostly ’time-limited’ , episodic disorder may amount to an underestimation of its severity and clinical burden.
We show that only a minority of depressed patients experienced early and sustained recovery from all affective and anxiety conditions, while the majority experienced a pattern of recurrent and often chronic episodes.
The long-term impact that such clinical courses have on a person’s level of functioning was confirmed by our clinical validation, where patients with chronic episodes had consistently higher levels of disability compared to those without chronic episodes and those who recovered .
Our study is unique because we have access to a large cohort of patients representing the full range of depression and anxiety disorders. The patients were rigorously diagnosed and followed for a longer period of time. Data were available throughout the 6-year follow-up period, allowing us to reliably categorize the different course trajectories.
| Conclusions |
Our data suggest that we may need to reconsider the prognosis of patients with MDD. The inclusion of symptoms from closely related disorders, such as (hypo)mania and anxiety, shows that the majority of patients have a chronic, disabling affective disorder and that full recovery is the exception rather than the rule.
Conceptualizing MDD as a narrowly defined, episodic disorder may underestimate both the prognosis of most of our patients and the type of appropriate care.
