Subthreshold depression in Parkinson's disease.
OBJECTIVE
It is estimated that 40% of patients with Parkinson's disease (PD) are clinically depressed, however, little is known about the frequency and associated features of subthreshold depression in PD. The current study sought to determine the prevalence of subthreshold depression (sD) and to further characterize the associated features in a sample of 111 nondemented patients with moderate to severe PD.


METHODS
Patients were classified into the following groups: diagnostic depression (DD), subthreshold depression (sD), or nondepressed (ND) by applying the Diagnostic and Statistical Manual, 4th edn criteria for depression and previously reported criteria for sD to items from the Beck Depression Inventory, 2nd edn. These groups were compared on clinical and demographic variables. The symptom profile of the sD group is also described.


RESULTS
Fifty participants (45.0%) were classified as ND, 32 (28.8%) as sD, and 29 (26.1%) as DD. Patients with sD were younger (approximately 5 yrs) than nondepressed patients, but did not differ in disease stage or any other demographic variables. Patients with sD tended to endorse mood symptoms that overlap with PD, including fatigue, sleep difficulties, appetite dysfunction, and concentration difficulties. These symptoms were also endorsed with high frequency by the other groups.


CONCLUSIONS
These findings suggest that sD is not uncommon in PD and may be more prevalent among younger patients. The finding that sD patients report mood symptoms that overlap with the PD symptomatology suggests that these two entities share common features and may be difficult to disentangle.
Nation
Daniel A
DA
Department of Psychology, University of Miami, Coral Gables, FL, USA.
Katzen
Heather L
HL
Papapetropoulos
Spyridon
S
Scanlon
Blake K
BK
Levin
Bonnie E
BE
D003866:Depressive Disorder / Q000145:classification / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000523:psychology*; D015995:Prevalence; D011569:Psychiatric Status Rating Scales; D011788:Quality of Life / Q000523:psychology; D012720:Severity of Illness Index