During puberty, adolescent girls show a dramatic increase in depressive symptoms, and by mid-teens girls are twice as likely to have depressive symptoms compared to boys. It has been suggested that this increase is controlled by the timing of puberty and, in particular, the onset of menarche; girls who experience puberty earlier may be more likely to experience more depressive symptoms compared to girls who experience it later. Although this link is seen in girls in their mid-teens, it is not clear if this association continues into later teenage years and later on, into adulthood. It is possible that girls who experience late menarche have a decreased risk of depressive symptoms into adulthood and therefore this late menarche may serve as a protective effect. However, girls who experience late menarche may show a 'catch-up' effect and eventually have similar levels of depressive symptoms compared to girls who have an earlier onset of menarche. There is a lack of research investigating the onset of menarche on depressive symptoms beyond teenage years, into adulthood. It is therefore important to investigate whether onset of menarche and the timing puberty explains some of the depressive symptoms seen in adult women. This would also aid in the understanding of the mechanism behind the link between puberty and depression including psychosocial and, hormone and neurological theories.