Link Between BMI (Body Weight) and Depression in Teens

Researchers explored the relationship between body weight and depression symptoms in teens and adults.

They found a link between higher body weight and increased depression, especially among teens.

Genetic factors appear to play only a small role.

Key Facts:

Teens who had higher body mass index (BMI) at age 12 were more likely to have more depression symptoms at age 16. The opposite was also true but the effect was weaker.
This bidirectional relationship was not seen in adults. In adults, depression did not clearly predict later BMI.
Genetic factors accounted for less than 20% of the link between BMI and depression. Most of the link appears to be due to environmental factors.

Source: Psychological Medicine 31 Aug 2023

The Link Between BMI and Depression in Teens

Researchers looked at data from over 7,000 pairs of twins in the UK who were followed from age 12 to age 21.

They had data on the teens’ BMI (weight adjusted for height) and depression symptoms at ages 12, 16, and 21.

They found that teens with higher BMI at age 12 tended to have more depression symptoms at age 16. The increase was small but consistent.

Every 1 unit increase in BMI at age 12 was linked to a 0.19 unit increase in depression symptoms at age 16.

The opposite relationship was also true – teens with more depression symptoms at age 12 had higher BMIs at age 16.

But this effect was weaker. Every 1 unit increase in depression at age 12 was linked to just a 0.01 unit increase in BMI at age 16.

Overall, the relationship between BMI and depression in the teen years appears to be bidirectional.

But early BMI seems to be a stronger predictor of later depression than the reverse.

The researchers did not see this bidirectional relationship continue into adulthood.

In their data, depression symptoms at age 16 did predict slightly higher BMI at age 21.

However, the reverse was not true – BMI at age 16 did not predict depression symptoms at age 21.

Other studies looking at adults have found mixed results.

Some show depression predicts future weight gain, while others do not.

More research is needed to clarify if depression contributes to weight gain in adults.

Using the twin data, the researchers estimated how much genetics influences the link between BMI and depression.

They found genetics accounted for less than 20% of the association.

For example, at age 16, genetics explained 17% of the link between BMI and depression.

The remaining 83% was due to environmental factors.

This suggests genes play only a small role in the weight-depression relationship.

The connection seems to arise largely from teens’ life experiences and environment.

Researchers have proposed several environmental mechanisms that might contribute to the link between excess weight and depression:

Weight stigma – Overweight youth are more likely to experience bullying and social isolation, which can lead to depression.
Body dissatisfaction – Higher weight is linked to poorer body image and self-esteem, which are risks for depression.
Unhealthy behaviors – Depression can cause changes in sleep, appetite, and activity that promote weight gain.
Emotional eating – Depression can lead to using food to cope with negative emotions.

The strength of these factors likely changes across development.

Weight stigma and body image concerns may play a bigger role in adolescence when self-identity is developing.

Depression symptoms might disrupt sleep and activity more as teens gain autonomy over health habits.

Identifying when these processes emerge could inform efforts to prevent both weight issues and depression.

This research yielded several key insights on the relationship between weight and depression:

The association strengthens through adolescence – links between BMI and depression symptoms were stronger at age 16 than age 12. Tackling weight and mood issues early may help break this connection as teens mature.
BMI more strongly predicts depression than vice versa – higher BMI was a better predictor of later depression symptoms than the reverse, especially in early adolescence. This highlights excess weight as a potential risk to monitor for emerging depression.
Genetics play a minor role – the weight-depression link was largely environmental, meaning life experiences and learned behaviors appear to drive the association. This suggests environmental changes could help break the connection.
Adult pattern may differ – depression did not clearly predict later BMI increases in adults as it did in teens. The dynamics linking weight and mood likely shift across development.

While many questions remain, this research helps map how weight and depression interrelate across life stages.

These insights can inform efforts to jointly prevent and treat weight issues and depression.

Catching signals early and tailoring solutions to age may help break the vicious cycle between excess weight and low mood.

In summary, this research explored the bidirectional relationship between body mass index (BMI) and depression symptoms in teens and adults.

It found evidence that higher BMI predicts increased depression in adolescence, while genetics appear to play only a minor role.

These insights can help inform efforts to jointly prevent and address weight issues and depression across the lifespan.

References

Study: The relationship between weight-related indicators and depressive symptoms during adolescence and adulthood: results from two twin studies
Authors: Ellen J Thompson et al. (2023)