EEG frontal lobe asymmetry as a function of sex, depression severity, and depression subtype

To investigate possible contributors to the inconsistent association between frontal lobe asymmetry (FLA) and
depression, EEG data were collected across five frontal sites, and examined for their associations with four
subtypes of depression (Depressed mood, Anhedonia, Cognitive depression, Somatic depression). One hundred
community volunteers (54 males, 46 females) aged at least 18 yr completed standardized scales for depression
and anxiety, and gave EEG data under Eyes Open and Eyes Closed conditions. Results indicated that, although
there was no significant correlation between the differences in EEG power across each of the five pairs of frontal
sites and total depression scores, there were several meaningful correlations (accounting for at least 10% of the
variance) between specific EEG site differences data and each of the four depression subtypes. There were also
different patterns of association between FLA and the depression subtypes according to sex, and total depression
severity. These findings help to explain the apparent inconsistency in previous FLA-depression results, and argue
for a more nuanced approach to this hypothesis.