["Criminal Behaviour and Mental Health, Volume 36, Issue 4, Page 157-164, August 2026. ", "\nABSTRACT\n\nBackground\nSerious drug crime involves a high level of risk and is often characterised as requiring a network of suitable and trustworthy collaborators. Although prior studies have focused on the importance of economic, social and work‐related factors for involvement in such crime, there has been less research into the mental health of the people involved.\n\n\nAims\nTo assess the prevalence of mental disorders in a full nationwide cohort of individuals convicted of serious drug crimes in Denmark (2001–2020), who were born after 1984 and had a personal national identification number.\n\n\nMethods\nWe compared four groups: large‐scale serious drug crime offenders sentenced to ≥ 5 years' imprisonment (n = 232); moderate‐scale serious drug crime offenders sentenced to under 5 years' imprisonment (n = 2955); offenders convicted only of small‐scale drug offences, such as low‐level supply, but never of serious drug crime (n = 7630); and sex‐ and age‐matched general population controls who had never been convicted of a serious drug crime (n = 3187). Mental disorders were identified using hospital and pharmacy registers.\n\n\nResults\nThe adjusted prevalence of any mental disorder was similar across offender groups (large‐scale: 32%, 95% CI [27%–38%]; moderate‐scale: 36%, 95% CI [34%–38%]; small‐scale: 36%, 95% CI [35%–37%]) and, in all three groups, was substantially higher than among controls (23%, 95% CI [22%–25%]). A similar pattern was observed for specific disorders.\n\n\nConclusions\nOur results challenge the assumption that engagement in serious drug crime requires skills and behaviours that are incompatible with having a mental disorder. We conclude that people with serious drug crime convictions are as likely as minor drug offenders to need mental health services and that people with mental disorders are vulnerable to recruitment into serious drug crime.\n\n"]