Monorhinal odor identification and depression scores in patients with seasonal affective disorder.
BACKGROUND
Visual and olfactory pathways are interconnected. Olfactory deafferentation unmasks photoperiodic responsiveness in some nonphotoperiodic animals such as laboratory rats. By analogy, we hypothesized that olfactory deficits may unmask seasonal rhythms in certain individuals, namely those with seasonal affective disorder (SAD). Since previous studies suggest lateralized hemispheric dysfunction in SAD, and since olfactory neurons' primary projections are largely ipsilateral, we assessed olfactory identification performance on both the right and left side of the nose.


METHODS
Twenty-four patients with SAD and 24 matched controls were studied using a phenyl ethyl alcohol detection threshold test bilaterally and the University of Pennsylvania Smell Identification Test unilaterally. Subjects rated their mood using the Self Assessment Mood Scale for SAD. Patients' testing was done in both 'depressed' and 'improved on light' states.


RESULTS
No difference in olfactory performance was found between patients and controls or between patients before and after light treatment. However, right-side identification scores were negatively correlated with 'typical' depression scores (r = -0.56, P = 0.006), while left-side olfactory scores were not. Atypical depression scores were unrelated to olfactory performance. Similar correlations emerged between the olfactory identification laterality quotient (Right - Left)/(Right + Left) and typical depressive scores (r = - 0.64, P < 0.001) and total depression scores (r = - 0.59, P < 0.004).


CONCLUSIONS
We studied a demographically heterogeneous sample and did not control for menstrual factors.


CONCLUSIONS
Our results add to previous evidence of lateralized hemispheric involvement in SAD and suggest that olfaction may be related to seasonal emotional rhythms in humans.
Postolache
T T
TT
Section on Biological Rhythms/NIMH, Bethesda, MD 20892-1390, USA. postolache@nih.gov
Doty
R L
RL
Wehr
T A
TA
Jimma
L A
LA
Han
L
L
Turner
E H
EH
Matthews
J R
JR
Neumeister
A
A
No
C
C
Kroger
H
H
Bruder
G E
GE
Rosenthal
N E
NE
D000328:Adult; D000339:Affect; D016022:Case-Control Studies; D003863:Depression / Q000145:classification / Q000523:psychology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009812:Odorants; D000857:Olfaction Disorders / Q000503:physiopathology*; D017440:Photoperiod; D016574:Seasonal Affective Disorder / Q000503:physiopathology / Q000523:psychology*; D012720:Severity of Illness Index; D012903:Smell / Q000502:physiology*