Recent findings indicate that frontal brain asymmetry may be a marker
of risk for depression. However, the psychological predispositions tha
t account for the linkage between frontal brain asymmetry and depressi
on are unclear. The approach-withdrawal hypothesis is the primary fram
ework that has been offered to account for the linkages between fronta
l brain asymmetry and emotion or emotional disorders. We review eviden
ce consistent with this hypothesis and suggest several directions for
its extension. One such direction is to constrain the approach-withdra
wal hypothesis by linking frontal brain asymmetry to the known functio
ns of the prefrontal cortex. On this basis, we propose that frontal br
ain asymmetry may be preferentially linked to regulatory processes tha
t promote the temporal continuity and shifting of motivational or emot
ional priorities and the suppression of interference by competing sour
ces of motivation or emotion. We review evidence from psychosocial and
neurobiological studies of depression that is broadly consistent with
these predictions. We emphasise the need for future studies directly
testing our hypotheses.