Daughters of women who gave birth after age 30 are more likely to experience the symptoms of depression, according to a new study. Surprisingly, sons of older mothers are unaffected and remain at the usual risk levels for anxiety.

“Older maternal age is associated with depression, anxiety, and stress symptoms in young adult females,” wrote the researchers, led by Jessica Tearne, a doctoral student at the University of Western Australia.

Psychologists have frequently studied how age affects a mother herself, even if their findings are mixed. For example, University of British Columbia researchers found the prevalence of depression was significantly higher in mothers between the ages of 40 and 44 than in mothers between the ages of 30 and 35. However, results from an investigation conducted at State University of Rio de Janeiro suggest the opposite; here the researchers observed older mothers were less prone to developing post-partum depression. Meanwhile, a Bergen University College study found Norwegian women 32 or older had only a slightly increased risk of psychological distress during the first 18 months of motherhood compared to women younger themselves.

A Special Relationship

This mixed bag of results from around the world suggests the current study may also be tentative... and possibly impacted by cultural differences. To conduct the research, Tearne and her colleagues analyzed data from the Western Australian Pregnancy Cohort Study. This longitudinal study recruited pregnant women between the years 1989 and 1991 and then assessed the psychological health of their 1,200 children at various ages over the next 23 years. Tearne and her colleagues looked at each child's self-reported levels of symptoms of depression, anxiety, and stress at age 20, and then the researchers compared this information to parental ages at the time of birth.

Father’s age had no effect on their children’s psychological well-being, the psychologists discovered. Similarly, 5 percent of the mothers were under age 20, yet this young maternal age did not impact their children. And, sons were generally unaffected by maternal age.

Only daughters felt the impact of their mother’s age. Daughters whose mothers were between 30 and 34 at time of birth reported significantly higher levels of stress when compared to daughters whose mothers were under age 30. Worse still, daughters whose mothers were over 35 had significantly higher levels of stress, depression, and anxiety.

Importantly, the authors caution the participants experienced only symptoms, which does not mean they suffered (or would progress to) clinical depression or other diagnosable mental disorders.

Tearne and her co-authors say their study results do not indicate a cause, yet they hypothesize a large age difference might negatively impact the mother-daughter relationship.

“It may be that a 30 or more year age difference between mother and daughter leads to a significant difference in the value systems that may cause tensions in the relationship,” Tearne said in a press release, adding these mother-daughter tensions lead to stress, worry, and sadness, particularly during the transition to young adulthood.

Alternately, the authors theorize women who gave birth over age 30 would be in their 50s when their children were assessed and so more likely to be experiencing health problems. Since past research suggests daughters (but not sons) are affected by their mother's health, this might also explain their symptoms.

Source: Tearne JE, Robinson M, Jacoby P, et al. Older Maternal Age Is Associated With Depression, Anxiety, and Stress Symptoms in Young Adult Female Offspring. Journal of Abnormal Psychology. 2015.