Teenage fertility has many consequences, one of which is its influence on the mental health of mothers. In this paper we compare the medium- to long-term mental health effects of four groups of women in Britain in the 1990s: teenage women who had first births, teenage nonmothers, and mothers of two older age groups. We study as well the effect of womens age at first birth on their psychological well-being and estimate the so-called pivotal age at first birth to determine at what age having a birth would change to from a bust to a boost to mental health. These aims are achieved by analyzing the first 10 waves the British Household Panel Survey (1991-2000). We find that teenage mothers tend to have a significantly higher level of depression in the medium term postpartum. More generally, within five years postpartum, no pivotal age at first birth is found, and estimated pivotal age at first birth begins to appear reasonable only from five to ten years postpartum. The results suggest that, while older mothers tend to have a smaller likelihood of depression than younger mothers, the effects are curvilinear, and that motherhood may not enhance a mothers well-being until the child is at least no longer a toddler.