ADHD a risk factor for serious mental health issues, finds study

By Melanie Hinze

ADHD, independent of other factors, appears to contribute to an increased risk of post-traumatic stress disorder (PTSD), anorexia and suicide attempts, research published in BMJ Mental Health suggests.

To determine whether ADHD was causally related to other psychiatric disorders, the researchers performed a two-sample network Mendelian randomisation analysis using a range of datasets. Initially, they aimed to establish links between ADHD and seven common mental health issues: major depressive disorder (MDD), bipolar disorder, anxiety disorder, schizophrenia, PTSD, anorexia nervosa and at least one suicide attempt. They then looked at whether these disorders were responsible for the effects seen in this first analysis. Lastly, they pooled their data to determine the total and direct effects of ADHD.

The researchers found that genetic liability to ADHD was independently associated with the risk of anorexia nervosa. A bidirectional relationship was seen between ADHD and MDD. After adjusting for MDD, ADHD was also seen to have a direct association with PTSD and suicide attempt. There was, however, no relationship with anxiety, bipolar disorder or schizophrenia.

Professor Dave Coghill, Financial Markets Foundation Chair of Developmental Mental Health in the Departments of Paediatrics and Psychiatry at the University of Melbourne, and Professor of Child and Adolescent Psychiatry, Royal Children’s Hospital Melbourne, said this was a complex but interesting paper.

‘We already know that people with ADHD are more likely to have a wide range of other mental health conditions including those that are looked at in this study – MDD, bipolar disorder, schizophrenia, anorexia nervosa and PTSD – and that suicide risk is higher in those with ADHD,’ he said. ‘What is not so clear is whether ADHD is part of the cause of these disorders.’

‘The Mendelian randomisation approach helps us understand whether there are causal relationships between different things,’ he explained. ‘So what the study says is that ADHD itself, independent of other factors, appears to contribute to the increased risk of PTSD, anorexia and suicide attempts.’ Professor Coghill added that MDD also increased the risk for suicide attempts and PTSD – independent of ADHD.

The researchers also found that ADHD and MDD had reciprocal causal relationships but there appeared to be no such causal relationships between ADHD and schizophrenia and ADHD and bipolar disorder. ‘From a clinical perspective these findings support the suggestion made in the Australian evidence-based guidelines for ADHD that clinicians who are working with a broad range of mental health disorders should always think about whether ADHD might be contributing to the clinical picture,’ Professor Coghill said.

BMJ Ment Health 2023; 26: 1-8; doi: 10.1136/ bmjment-2022-300642.