ADHD & Criminality

Exploring the link between ADHD, criminal behaviour, and the failings of the criminal justice system

In May 2025, NHS England published statistics that suggested around 2,498,000 in England have ADHD (Attention Deficit Hyperactivity Disorder), including those without a formal diagnosis. It is estimated that 741,000 of those are children and young people aged 5-24.

These figures highlight the increasing need for early diagnosis, access to treatment, and ongoing legal and mental-health support for individuals with ADHD — particularly those who may later come into contact with the criminal justice system.

ADHD and the Criminal Justice System

According to a report published by The Justice Gap, around 25% of prisoners in Britain are thought to have ADHD — a condition described as “critically underdiagnosed.”

The study found a strong correlation between ADHD and criminal behaviour, noting an increase in early-age criminality, impulsivity, and reoffending rates among affected individuals. Prisoners with ADHD are also up to eight times more likely to be involved in aggressive incidents and face a higher risk of co-occurring psychiatric disorders.

The same research estimated that better recognition and management of ADHD in prisons could reduce criminality by 32% in men and 41% in women, saving the UK Criminal Justice System approximately £11.7 million annually.

These findings reinforce the importance of specialist legal representation and rehabilitation pathways tailored for defendants with ADHD.

Supporting evidence from medical research

The British Medical Journal (BMJ) recently published a study titled “ADHD drug treatment and risk of suicidal behaviours, substance misuse, accidental injuries, transport accidents, and criminality.”

It confirms that ADHD affects approximately 5% of children and 2.5% of adults worldwide, and is linked to a range of adverse behavioural outcomes, including criminality and substance misuse.

The Justice Gap also found that 96% of prisoners with ADHD have an additional mental-health condition, such as substance use, conduct, or personality disorder.

Together, these findings expose a systemic failure within both healthcare and the justice system to identify and manage ADHD effectively — a failure that continues to impact defendants, victims, and society.

How the law differentiates defendants with ADHD

In the UK, ADHD is recognised as a disability under the Equality Act 2010, meaning defendants are entitled to reasonable adjustments during legal proceedings.

For cases funded by the Legal Aid Agency, law firms can apply for intermediary support to assist defendants with ADHD. Under Section 4-117a of Archbold 2025, a Ground Rules Hearing must be held to set out procedures ensuring the defendant’s effective participation in court.

The court may also direct the jury on the defendant’s communication needs, attention difficulties, or impulsive behaviours, and rely on intermediary reports for fair trial outcomes.

These protections demonstrate the critical need for experienced criminal defence solicitors familiar with ADHD and its impact on behaviour and comprehension during proceedings.

Sentencing guidelines for offenders with ADHD

The Sentencing Council’s guidelines, effective from October 2020, require courts to consider the presence of mental or neurological impairments — including ADHD — when determining culpability and sentencing. However, as the guidelines note, such impairments do not automatically reduce sentences, but rather guide judges in assessing the context of offending behaviour.

For defendants with ADHD, legal representatives should ensure medical and psychiatric reports are submitted to the court before sentencing to evaluate the associated risks and inform rehabilitation plans. Where custodial sentences are imposed, courts must forward relevant psychological and health reports to the prison under Rule 28.9 of the Criminal Procedure Rules.

What can parents do if their child has ADHD and faces criminal proceedings?

For parents of children or young adults with ADHD, involvement with the criminal justice system can be deeply distressing. Parents play a crucial role in ensuring that their child receives appropriate support and understanding at every stage of the legal process — beginning at the police station.

Not all adults with ADHD show immediate signs of vulnerability, and each person will display different indicators. Some symptoms may be clear — such as impulsivity, distractibility, or emotional sensitivity — while others are much harder to detect. If the police are unaware of the condition, the detainee may not receive an appropriate adult, which can negatively affect both the interview process and case outcome.

A parent can act as their child’s appropriate adult during a police interview, whether their child is a youth or an adult. This role is vital in safeguarding the rights and welfare of the person being questioned, ensuring that they understand the process, and that any communication difficulties caused by ADHD are properly addressed.

Early diagnosis of ADHD is essential

As all criminal cases begin at the police station, the process of supporting defendants with ADHD must start there. Early recognition, the presence of an appropriate adult, and representation from a criminal defence solicitor experienced in ADHD-related cases can make a significant difference in how the case progresses and how fairly the individual is treated.

Simple steps include ensuring access to an appropriate adult, requesting an intermediary assessment, and seeking advice from a criminal defence solicitor experienced in ADHD cases.

You can find some more specific help if your child has been arrested in our dedicated area on youth crime, https://mk-law.co.uk/youth-crime

Is the system designed to support defendants with ADHD?

While policies exist to support defendants with ADHD, they are often inconsistently applied. In March 2025, NHS England estimated that 549,000 people were waiting for an ADHD assessment — an increase of 13.5% from the previous year. Of these, 316,000 were children, many waiting more than a year for diagnosis.

A study by NHS Berkshire Healthcare found that for women undiagnosed in childhood, the average age of diagnosis is 36–38, indicating that many adults enter the justice system without ever receiving adequate support or treatment.

This lack of early intervention creates a cycle of undiagnosed ADHD, unmanaged symptoms, and criminal justice involvement, which could be mitigated through better healthcare and targeted legal support.

The economic and social cost of inaction

The consequences of untreated ADHD extend far beyond individual cases.

According to Paulette Hamilton MP, the economic cost of not treating ADHD is estimated at £17 billion annually — covering lost productivity, social services, and criminal justice costs.

This figure highlights the urgent need for coordinated reform between healthcare providers, education systems, and the justice sector to prevent ADHD from escalating into criminal behaviour.

Conclusion: A call for change

The link between ADHD and criminality is undeniable — but preventable. Early diagnosis, ongoing treatment, and fair representation within the justice system are key to reducing reoffending rates and supporting rehabilitation.

For anyone facing criminal proceedings where ADHD may be a factor, it is vital to seek guidance from specialist criminal defence solicitors who understand how ADHD affects behaviour, responsibility, and participation in legal processes.

Rebecca Applegarth paralegal at MK Law

These statistics are truly alarming.

ADHD is not an inevitable hindrance, but it can be an isolating and debilitating condition. Where necessary, vulnerable defendants will require additional provisions throughout their proceedings that should not be overlooked.

ADHD Awareness Month throughout October serves as a vital reminder that awareness must lead to reform. True justice means recognising the needs of individuals with ADHD and ensuring that every stage of the legal process reflects fairness, empathy, and understanding.