2D:4D digit ratio predicts depression severity for females but not for males

• Females had higher depression scores and higher digit ratios compared to males.
• The relationship between digit ratio was significant for females but not for males.
• The relationship between digit ratio and depression for females is small.
• The relationship is not consistent across depression measures.

Depression affects at least twice the number of women than men. This difference appears to be relatively consistent across a wide range of cultures, with an average female to male ratio of 2:1 (Immerman & Mackey, 2003). Explanations of this sex difference have focused on hormones, the role that early traumas such as sexual abuse play in predisposing females to depression, and socialization influences (Nolen-Hoeksema, 1998). Digit ratio (2D:4D index to ring finger) is a well-established sexually dimorphic trait in humans, with females having a higher ratio than males (Martin, Manning, & Dowrick, 1999). This trait, stable across the lifetime, has been correlated with many other sexually dimorphic traits (Austin, Manning, McInroy, & Matthews, 2001). Previous research has shown contradictory results regarding whether depression is associated with a more masculine digit ratio or a more feminine digit ratio. The purpose of this study was to further investigate whether digit ratio is predictive of severity of depression. Results indicated that higher digit ratio is correlated with higher depression scores in females, but not males. Study limitations and further directions are considered.