Obesity is linked with an increased risk of developing anxiety and depression in children and adolescents, independent of traditional risk factors such as parental psychiatric illness and socioeconomic status, according to new research being presented at this year's European Congress on Obesity (ECO) in Glasgow, UK (28 April-1 May).

The nationwide study comparing over 12,000 Swedish children who had undergone obesity treatment with more than 60,000 matched controls found that girls with obesity were 43% more likely to develop anxiety or depression compared to their peers in the general population. Similarly, boys with obesity faced a 33% increased risk for anxiety and depression compared to their counterparts.

"We see a clear increased risk of anxiety and depressive disorders in children and adolescents with obesity compared with a population-based comparison group that cannot be explained by other known risk factors such as socioeconomic status and neuropsychiatric disorders," says Ms. Louise Lindberg from the Karolinska Institutet, Stockholm, Sweden who led the research. "These results suggest that children and adolescents with obesity also have an increased risk of anxiety and depression, something that healthcare professionals need to be vigilant about."

Anxiety and depression are reported to be more common in children with obesity than in children of normal weight, but it is unclear whether the association is independent of other known risk factors. Previous studies are hampered by methodological limitations including self-reported assessment of anxiety, depression, and weight.

To provide more evidence, researchers from the Karolinska Institutet in Sweden conducted a nationwide population-based study to investigate whether obesity is an independent risk factor for anxiety or depression. 12,507 children aged 6-17 years from the Swedish Childhood Obesity Treatment Register between 2005 and 2015 were compared to 60,063 controls from the general population matched for sex, year of birth, and living area.

The research team adjusted for a range of factors known to affect anxiety and depression including migration background, neuropsychiatric disorders, parental psychiatric illness, and socioeconomic status. A total of 4,230 children and adolescents developed anxiety or depression over an average of 4.5 years.

Obesity was clearly linked with higher risk of anxiety and depression in childhood and adolescence. Girls (11.6% vs 6.0%) and boys (8.0% vs 4.1%) with obesity were more likely to be diagnosed with anxiety and depression than those in the general population over the study period.

In further analyses, excluding children with neuropsychiatric disorders or a family history of anxiety or depression, the risks were even higher. In particular, boys with obesity were twice as likely to experience anxiety or depression as their normal-weight peers -- whilst girls with obesity were 1.5 times more likely.

"Given the rise of obesity and impaired mental health in young people, understanding the links between childhood obesity, depression and anxiety is vital," says Ms. Lindberg. "Further studies are needed to explain the mechanisms behind the association between obesity and anxiety/depression."

The authors acknowledge that this is an observational study and cannot prove that obesity causes depression or anxiety but only suggests the possibility of such an effect. They point to several limitations including that there is no weight and height data in the comparison group; unmeasured confounding may have influenced results; and that rates of anxiety and depression may be underestimated since a large proportion of individuals suffering from these conditions do not seek medical care.