Half of people arrested in London may have undiagnosed ADHD, study finds

(Press-News.org) Offering screening for neurodivergence to people detained by the police could help ensure access to appropriate support and fairer treatment in the criminal justice system, say Cambridge researchers, after a study suggests that one in two individuals arrested and detained in London may have undiagnosed attention-deficit/hyperactivity disorder (ADHD) and one in 20 may have undiagnosed autism.

Research has consistently found that neurodivergent individuals – particularly autistic people and those with ADHD – are overrepresented within prison populations. There is also growing evidence of undiagnosed ADHD and autism among individuals in contact with the criminal justice system. However, estimates of the prevalence of the conditions within these settings differ.

Dr Tanya Procyshyn, a research associate at the Autism Research Centre at the University of Cambridge, said: “To ensure fair treatment in the criminal justice system, we need to understand how neurodivergence affects interactions with the law. This can help avoid unnecessary criminalisation of misunderstood behaviour and ensure that potentially vulnerable individuals are able to access appropriate support.”

Dr Procyshyn and Dion Brown, a senior Detective from the Metropolitan Police Service, co-led a study to explore the feasibility of screening arrested individuals for traits related to ADHD and autism and to examine the reason leading to the arrest.

Over an eight-week period in 2024, people detained at six London Metropolitan Police custody centres were offered voluntary screening for ADHD and autism carried out on-site by a healthcare professional, detention officer, or arresting police officer.

ADHD traits were assessed using a modified version of the Adult ADHD Self-Report Scale. Autistic traits were assessed using the 10-item Autism-Spectrum Quotient. Although these tools are not diagnostic, they provide a practical method to flag individuals who may benefit from further assessment.

The results are published today in Criminal Behaviour and Mental Health.

The majority of the 303 eligible individuals arrested (71%) consented to screening. Individuals who screened above the thresholds for ADHD or autistic traits were informed and given additional information on how to seek a formal diagnosis.

Eight per cent of arrested individuals had an existing diagnosis of ADHD, which is slightly higher than the prevalence of ADHD in the general population (5%). However, an additional one in two people (50%) without an existing ADHD diagnosis scored at or above the threshold for possible undiagnosed ADHD. Strikingly, this included 33 individuals (17%) whose scores suggested a very high number of ADHD traits.

Nine individuals (4.2%) had an existing autism diagnosis, which again is slightly higher than the prevalence of autism in the general adult population (3%). An additional 5.4% scored at or above the threshold for possible undiagnosed autism.

Regarding the reason leading to the arrest, six in 10 individuals (60%) arrested for drug offences had an existing diagnosis or positive screening result for ADHD. Previous studies have found that some neurodivergent individuals may self-medicate with illegal substances. Several studies have also reported that people with ADHD are less likely to engage in criminal behaviour when taking medication for ADHD, and this effect is thought to reflect improved impulse control.

Dion Brown, a senior Detective from the Metropolitan Police Service, said: "Screening for ADHD and autism at the first point of contact with law enforcement benefits both the criminal justice system and the individuals involved.

“Early identification helps officers interpret behaviours that might otherwise be misunderstood and ensures appropriate support is provided. This approach creates opportunities to divert vulnerable individuals away from the criminal justice process and towards the help they may need.”

Professor Sir Simon Baron-Cohen, Director of the Autism Research Centre at Cambridge, and a member of the team, added: “Screening for possible neurodivergence will allow more informed legal decision-making, taking into account cognitive and communicative differences. It can also help ensure defendants get access to legal protection and appropriate counsel. This could improve both the treatment and experiences of neurodivergent people in the criminal justice system and ultimately lead to fairer outcomes, including protection under the law, which is a basic human right.”

The research was funded by the Wellcome Trust.

Reference

Brown, D & Procyshyn, TL et al. Neurodiversity in custody: Screening results for ADHD and autistic traits in individuals arrested by the London Metropolitan Police. Criminal Behaviour and Mental Health; 10 Dec 2025

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