Depression occurring before 40 years of age is associated with a longer duration of symptoms, more childhood trauma, and increased suicidal thoughts, compared with depression that begins later in life.
Indeed, "When performing diagnostics it is important to take into account that some symptoms may not occur as much at a higher age of depression onset, [although] a diagnosis may be present," wrote Dr. Nicole C.M. Korten and her colleagues in the May issue of the Journal of Affective Disorders.
"Additionally, the more personal vulnerability and chronic character of early onset depression are important factors to keep in mind for prevention and treatment strategies," they added (J. Affect. Disord. 2012;138:259-67).
Dr. Korten, of the VU University Medical Center, in Amsterdam, looked at data from the baseline assessment of 1,104 subjects enrolled in the Netherlands Study of Depression and Anxiety, an 8-year longitudinal cohort study, according to the authors.
All subjects had to have a current (within 6 months of the assessment) DSM-IV diagnosis of major depressive disorder, as well as information about the age of onset.
Symptoms of depression were assessed using the Composite International Diagnostic Interview (CIDI), with three general depressive symptoms on the DSM-IV split up into more specific descriptors: "appetite/weight change" was broken into increased vs. decreased appetite/weight; "sleep problems" was changed to insomnia vs. hypersomnia; and "psychomotor change" became retardation vs. agitation.
An assessed "duration of symptoms," in months, referred to the 4 years preceding the baseline assessment.
The overall mean age of the sample was 40.8 years; slightly less than one-third were male (32.3%).
The authors found, using a continuous age of onset indicator ranging from 4 to 64 years and adjusting for socio-demographic factors, late onset depression was associated with less sadness (P less than .001), less weight gain and fewer increases in appetite (P = .008), more weight loss and a suppressed appetite (P less than .007), fewer feelings of worthlessness (P = .01), less diminished concentration (P = .04), and fewer thoughts of death (P less than .001).
An older age of onset also was tied to a shorter duration of symptoms (P less than .001), not committing a serious suicide attempt (P less than .001), and a lower severity of depression (P = .005).
Finally, regarding the presence of comorbidities, a higher age of onset was less often associated with generalized anxiety disorder (P = .02), social phobia (P = .02), and dysthymia (P = .001).
Next, the authors analyzed early vs. late onset depression characteristics using a dichotomous model, with 40 years as the cutoff.
In this set, 80.2% of subjects were classified as having early onset disease, with a mean age of onset of 22.2 years. The remaining late onset subjects had a mean age of onset of 46.8 years.
Looking at demographic data, "As expected, [late onset depression] was associated with a higher age (odds ratio, 1.16; 95% confidence interval, 1.13-1.18), but [late onset depression] also was associated with [fewer] years of education (OR, 0.91; 95% CI, 0.86-0.96) and being male (OR, 1.67; 95% CI, 1.16-2.39)," the researchers wrote.
Characterizing according to symptomatology, the researchers found that feelings of sadness (OR, 0.41; 95% CI, 0.19-0.86) were less often observed in late onset disease.
"The psychosocial factors [like] childhood events (OR, 0.77; 95% CI, 0.68-0.88), family history (OR, 0.60; 95% CI, 0.38-0.95), and neuroticism (OR, 0.94; 95% CI, 0.91-0.97) were less often observed in late onset depression," added the researchers, "in line with the continuous age of onset analysis."
The authors stated that one major limitation of this study was the potential for recall bias among patients, since onset was assessed retrospectively.
They pointed out, however, that other studies reported high test-retest reliability of self-reported age of onset of major depression, and added that "although the exact onset point may sometimes be uncertain, participants can likely recall whether symptoms started earlier or later in life."
In conclusion, wrote Dr. Korten, the "subtle but consistent differences" observed in the current study confirm that "early onset depression might be a more chronic form of depression with probably a worse course."
She cautioned that the findings must be confirmed in further longitudinal analysis.
The authors stated that they had no conflicts of interest and disclosed no commercial funding.