J. O'Brien et al., Cognitive impairment in depression is not associated with neuropathologic evidence of increased vascular or Alzheimer-type pathology, BIOL PSYCHI, 49(2), 2001, pp. 130-136
Background: Cognitive impairment is common in depression, but underlying me
chanisms remain unknown. We examined whether increases in Alzheimer-type or
vascular pathology are associated with cognitive impairments in elderly de
pressed subjects.
Methods: Eleven subjects who had died during a well-documented episode of D
SM-IV major depression were included Neuropathologic assessments, blind to
group membership, included standardized assessment of neuritic plaques, neu
rofibrillary tangles, and Lewy Bodies in frontal, temporal, parietal, and o
ccipital cortices. Braak staging of Alzheimer pathology was also performed
Cerebral microvascular disease was scored according to a previously validat
ed scale, and a score for cerebral and systemic atheroma of large and mediu
m sized arteries was obtained.
Results: No subject had Lewy bodies. Plaque and tangle counts for all subje
cts were well within published norms for age-marched control subjects. Ther
e were no significant differences in plaque or tangle counts between subjec
ts who were cognitively impaired (n = 5) and those who were nonimpaired (n
= 6) during their depressive illness. Similarly, neither total microvascula
r pathology nor deep frontal microvascular pathology differed between the t
wo groups.
Conclusions: Our results indicate that the liability for some patients to d
evelop cognitive impairment during a depressive episode is not related to a
n increase in Alzheimer-type or vascular neuropathologic change. This indic
ates that other mechanisms must underlie both the cognitive impairment asso
ciated with depression and the observation that depression is a risk factor
for dementia. (C) 2001 Society of Biological Psychiatry.