Obesity found to increase risk of mental disorders

Obesity affects more than 670 million people worldwide, with extensive research proving that the disease promotes metabolic disorders and serious cardio-metabolic complications such as diabetes mellitus, arterial hypertension and dyslipidaemia. But according to a new study published in the journal Translational Psychiatry, people suffering from obesity are also at a significantly greater risk of developing mental disorders.

Researchers from the Medical University of Vienna and the Complexity Science Hub Vienna analysed a population-based dataset of all inpatient hospitalisations in Austria from 1997 to 2014 in order to determine the relative risks of concomitant diseases in obesity and to identify statistically significant gender differences. Consequently, it became evident that an obesity diagnosis significantly increases the probability of a broad spectrum of mental disorders in all age groups — including depression, nicotine addiction, psychosis, anxiety and personality disorders.

“In order to find out which illness typically appeared prior and subsequently to the obesity diagnosis, we had to develop a new method,” said co-first author Elma Dervic, from the Complexity Science Hub. “This allowed us to determine whether there are trends and typical patterns in the occurrence of diseases.”

In case of all co-diagnoses, with the exception of the psychosis spectrum, obesity was in all likelihood the first diagnosis made prior to the manifestation of a psychiatric diagnosis. Until now, physicians often assumed that psychopharmacological drugs were the cause for the link between mental disorders and diabetes.

“This may be true for schizophrenia, where we see the reverse chronological order, but our data does not support this for depression or other psychiatric diagnoses,” said first author Alexander Kautzky, from MedUni Vienna. However, whether obesity directly affects mental health or whether early stages of psychiatric disorders are inadequately recognised is not yet known.

Surprisingly, the researchers found significant gender differences for most disorders, with women showing an increased risk for all disorders except schizophrenia and nicotine addiction. While 16.66% of all obese men also suffer from nicotine addiction, this is only the case in up to 8.58% of obese women. The opposite is true for depression: the rate of diagnosed depressive episodes was almost three times higher in obese women (13.3% obese, 4.8% non-obese). Obese men were affected twice as often (6.61% obese, 3.21% non-obese).

With the study showing that obesity often precedes severe mental disorders, on top of metabolic disorders, the findings underscore its importance as a pleiotropic risk factor for health problems of all kinds. This is primarily true for young age groups, where the risk is most pronounced. For this reason, the researchers believe that thorough screening for mental health problems in obese patients is urgently needed to facilitate prevention or ensure that appropriate treatment can be given.

“From a clinical point of view, these results emphasise the need to raise awareness of psychiatric diagnoses in obese patients and, if necessary, to consult specialists at an early stage of diagnosis,” said study leader Michael Leutner from MedUni Vienna.

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