Table 1: Distribution of the 5-HTTLPR variants; demographic, clinical, and neuropsychological data for major depressive disorder (MDD) and control groups.

MDD
( )
Controls
( )
Statistics value Effect size
(Cohen’s )

5-HTTLPR S/L allele12/713/6 0.732
Gender, female/male15/414/5 0.703
Age, years (range 18–56)34.8 (12.7)36.0 (15.8) 0.7970.08
Education, years13.4 (2.4)14.7 (2.8) 0.1500.50
Duration of illness, years (range)8.1 (8.0)
Number of depressive episodes2.3 (1.6)

Self-ratings:
 HDRS24.0 (3.7)
 BDI total score, range 0–6032.6 (11.8)1.2 (1.6) <0.0014.69
 BHS total score, range 0–6312.5 (5.0)1.9 (0.9) <0.0013.59
 BAI total score, range 0–2019.5 (10.6)1.9 (1.2) <0.0012.98

Neuropsychological tests:
 Abstract reasoning
  Similarities 26.8 (3.7)27.3 (3.0) 0.7000.15
  Block design 34.5 (7.6)39.5 (8.6) 0.0290.62
 Episodic memory
  Logical memory I22.3 (8.6)27.4 (5.4) 0.0370.73
  Logical memory II19.7 (8.4)25.0 (4.9) 0.0280.80
  Verbal paired associates I18.6 (4.7)20.7 (2.6) 0.0890.58
  Verbal paired associates II6.8 (1.6)7.4 (0.9) 0.1070.48
  Visual reproduction I33.3 (3.7)38.6 (2.1) <0.0011.83
  Visual reproduction II 32.5 (5.1)37.7 (2.9) <0.0011.30
 Working memory
  Visual memory span 18.3 (2.9)19.6 (2.4) 0.1330.49
  Letter number sequencing10.5 (2.4)11.3 (2.0) 0.2800.36
 Executive functioning
  Trail making test B sec.74.1 (21.6)71.3 (26.9) 0.6970.12
  Stroop color-word sec.109.5 (21.3)104.9 (30.2) 0.5870.18
  Semantic fluency 23.2 (6.3)26.5 (5.1) 0.0860.58
  Letter fluency 16.8 (3.9)18.3 (3.7) 0.2900.39
 Processing and motor speed
  Trail making test A sec.37.6 (10.8)31.4 (8.0) 0.0263.96
  Stroop color naming73.1 (11.7)63.5 (10.2) 0.0120.88
  Digit symbol (WAIS-R)57.6 (11.9)63.5 (12.1) 0.0900.49
  Finger tapping, dominant47.5 (4.6)51.1 (6.1) 0.0330.67
  Finger tapping, nondominant41.7 (5.1)45.5 (4.4) 0.0220.80

The results are given as mean (SD), except for gender and 5-HTTLPR variants, for which the results are given as frequency. Group comparisons in neuropsychological tests were analyzed with MANCOVA in which gender and age were covariates.
HDRS: Hamilton Rating Scale for Depression; BDI: Beck’s Depression Inventory; BHS: Beck’s Hopelessness Scale; BAI: Beck’s Anxiety Inventory.