People with chronic inflammatory bowel diseases (IBD) are more likely to develop mental illnesses. A large Swedish study now shows that this increased risk does not begin only after diagnosis but already years before. The findings provide new evidence that the mental health of those affected should be considered more early on.

Increased Risk for Mental Illnesses

According to the new study, the risk for mental illnesses increased two to three years before the diagnosis of a chronic inflammatory bowel disease (Crohn’s disease, ulcerative colitis, or an unspecified IBD). Depression, anxiety disorders, and substance abuse were particularly common. In contrast, there was no significant increase in risk for conditions such as schizophrenia, psychoses, or ADHD.1

How the Study Was Conducted

The researchers aimed to determine when the increased risk for mental illnesses begins in people with chronic inflammatory bowel diseases and how long it lasts. They analyzed Swedish health registers and compared nearly 44,000 people with a newly diagnosed IBD to around 179,000 individuals from the general population.

Additionally, more than 26,000 affected individuals were compared with their healthy siblings to examine the influence of shared genetic and familial factors. Mental illnesses were analyzed in the five years before and up to ten years after the IBD diagnosis. The results of the analysis were published in the journal “Clinical Gastroenterology and Hepatology.”

The Results in Detail

Two years before the diagnosis, the risk for a psychiatric disorder was already increased. Shortly after the diagnosis, the highest level was reached. Although the risk decreased afterward, it remained above the level of the comparison groups even ten years later.

During an average follow-up period of 7.4 years, 16.5 percent of patients with IBD developed a mental illness. In the control group, it was 12.8 percent. Anxiety disorders (7.3 versus 5.3 percent), depression (4.6 versus 3.2 percent), and substance abuse (3.3 versus 2.7 percent) were particularly common.

The strongest increases in risk were observed for depression and anxiety disorders. However, there was no significant increased risk for psychoses, schizophrenia, personality disorders, or ADHD. Nevertheless, shortly after diagnosis, affected individuals showed an increased risk for autism spectrum disorders and, from the fifth year onward, for eating disorders.

Notably, the sibling analysis showed a very similar risk pattern, albeit with slightly lower values. This suggests that shared genes or familial influences cannot fully explain the connection.

The age at diagnosis also plays an important role: While the increased risk before diagnosis was mainly observed in adults, patients who develop IBD in childhood or adolescence carry the highest absolute risk for later mental health issues in the long term.

Strengths and Weaknesses of the Study

The strengths of the study include the large number of participants, nationwide data collection, long follow-up period, and the use of validated registry data. Additionally, a sibling analysis reduced the influence of shared familial factors.

Limitations include the lack of data from primary care, information on disease activity, medications taken for IBD (which can also have psychological side effects), and lifestyle factors. As a result, milder mental illnesses may have been underestimated. Furthermore, it is an observational study, so no conclusions about cause and effect can be drawn.

Also of interest: Symptoms that indicate Crohn’s disease 

What Previous Studies Show on This Topic

A Danish study with over 22,000 IBD patients and more than 110,000 comparison individuals reached a similar conclusion in 2023.2 The risk for anxiety disorders and depression was already increased at least five years before diagnosis and remained so for at least ten years afterward. The highest risk was also around the time of diagnosis. However, the researchers found no connection for bipolar disorders.

A British analysis of primary care data suggests what might cause the early increase. It compared over 15,000 IBD cases with a control group.3 An increased IBD risk was only observed in people who had gastrointestinal complaints before depression. Depression alone was not associated with later IBD. This suggests that the psychological burden is more likely a consequence of undiagnosed gastrointestinal complaints rather than their cause–and aligns with the Swedish authors’ recommendation to include psychological symptoms in the initial gastroenterological assessment.

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