Depression and anxiety are common conditions in adolescence that can lead to persistent and life-long mood and anxiety disorders for some people.
One theory is that prenatal maternal stress can contribute to depression in young people (the so called fetal programming hypothesis).
The notion here is that pregnant women who experience stress may send messages to their foetus that are intended to help prepare it for a hostile environment. If the environment the child actually experiences is different from what they were prepared for, they can struggle to adjust.
Animal studies in rats and monkeys have supported the links between prenatal stress and depression, so many researchers are interested in exploring whether this link also exists in humans.
A new prospective study from researchers in Canada looks at whether adolescents born at high or low birth weights are more likely to experience symptoms of depression and anxiety after experiencing stress.
The researchers followed 3,732 adolescents from the National Longitudinal Survey of Children and Youth who were assessed for depression and anxiety in 2006−2007 and who had birth weight data available when the study began in 1994.
They defined low birth weight as babies in the bottom 10% of Canadian sex-specific standards for weight. High birth weight were those in the top 10%.
Symptoms of depression and anxiety were assessed when the young people were 12-15 years old, but these were measured using a self-reporting questionnaire rather than a clinical instrument, so this may have not given accurate results.
Major stressful life events and chronic stressors were reported throughout childhood. These included:
- The death of a parent or family member
- Parental conflict, divorce or separation
- Illness or injury to the child or a family member
- Abuse or fear of abuse
- A change in household members
- Substance misuse or mental illness in the family
- Other traumatic events such as the death of a pet or problems at school
- Low socioeconomic status
- Low social support from peers
- The authors adjusted for acute and chronic stress and found that compared with adolescents who were born at a weight appropriate for their gestational age, both low and high birth weights were associated with an increased risk of depression and anxiety in adolescence:
- Low birth weight (Odds ratio 1.50; 95% CI 1.08 to 2.08)
- High birth weight (OR 1.31; 95% CI 0.99 to 1.72)
- They examined boys and girls and found that the association was only significant for male adolescents (OR 1.64, 95% CI 1.06 to 2.53)
- Low social support was also associated with increased risk of depression and anxiety in adolescence (OR 2.70, 95% CI 2.22 to 3.27)
The authors concluded:
High birth weight and low birth weight children are at an increased risk for symptoms of depression and anxiety in adolescence.
The relation between chronic stress and depression or anxiety was stronger in low birth weight males, compared with normal birth weight males, supportive of the fetal programming hypothesis.
This is a well conducted prospective study with a large sample size, but it has some limitations. It’s worth noting that low birth weight is a proxy measure for prenatal stress, so it may in fact be an indicator of other factors.
So what can be done to help young people who are affected in this way? Well clearly, we can start with the pregnant mother and ensure that she has all of the social, psychological and nutritional support she needs to minimise the incidence of stress. Preventative depression programmes could be targeted at the at high risk population (low birth weight boys) and more can always be done to provide young people with the secure family background and coping skills they need to be more resilient to stress and anxiety.
Colman I, Ataullahjan A, Naicker K, Van Lieshout RJ. Birth Weight, Stress, and Symptoms of Depression in Adolescence: Evidence of Fetal Programming in a National Canadian Cohort.
Can-J-Psychiatry 2012;57(7):422–428. [PubMed abstract]