Although lower levels of omega-3 polyunsaturated fatty acids (PUFAs) are found in major depressive disorder, less is known about PUFA status and anxiety disorders.

Medication-free participants with DSM-IV-defined major depressive disorder (MDD), with (n = 18) and without (n = 41) comorbid DSM-IV anxiety disorders, and healthy volunteers (n = 62) were recruited from October 2006 to May 2010 for mood disorder studies at the New York State Psychiatric Institute. Participants were 18-73 years of age (mean age, 35.8 ± 12.6 years). Depression and anxiety severity was assessed using depression and anxiety subscales from the 17-item Hamilton Depression Rating Scale. Plasma PUFAs eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) and the ratio of arachidonic acid (AA; 22:4n-6) to EPA (AA:EPA) were quantified. This secondary analysis employed analysis of variance with a priori planned contrasts to test for diagnostic group differences in log-transformed PUFA levels (logDHA, logEPA, and logAA:EPA).

Plasma levels of logDHA (F2,118 = 4.923, P = .009), logEPA (F2,118 = 6.442, P = .002), and logAA:EPA (F2,118 = 3.806, P = .025) differed across groups. Participants with MDD had lower logDHA (t118 = 2.324, P = .022) and logEPA (t118 = 3.175, P = .002) levels and higher logAA:EPA levels (t118 = -2.099, P = .038) compared with healthy volunteers. Lower logDHA (t118 = 2.692, P = .008) and logEPA (t118 = 2.524, P = .013) levels and higher logAA:EPA levels (t118 = -2.322, P = .022) distinguished anxious from nonanxious MDD. Depression severity was not associated with PUFA plasma levels; however, anxiety severity across the entire sample correlated negatively with logDHA (rp = -0.22, P = .015) and logEPA (rp = -0.25, P = .005) levels and positively with logAA:EPA levels (rp = 0.18, P = .043).

The presence and severity of comorbid anxiety were associated with the lowest EPA and DHA levels. Further studies are needed to elucidate whether omega-3 PUFA supplementation may preferentially alleviate MDD with more severe anxiety.