11.1.2 Specific mental disorders and crime

How a disorder can relate to an offence

• Group statistics generate hypotheses about a person but do not decide what that person did, so set symptoms against the offence timeline.

• Previous violence is a historical factor: it informs the formulation but cannot be changed, unlike active symptoms, substance use or housing.

Mental disorder in prisons and police custody

• Personality disorder, chiefly antisocial personality disorder, is the most prevalent psychiatric diagnosis among prisoners, and its criteria overlap with the behaviour that leads to imprisonment.

• Antisocial personality disorder is present in just under half of male prisoners (about 47%, and 49% of sentenced men in the 1997 Office for National Statistics prisoner survey), far above the community rate.

• Antisocial personality disorder is the most prevalent mental disorder in male prisoners, ahead of alcohol misuse or dependence at 18 to 30%.

• The next most frequent personality disorders in men in prison in England and Wales, paranoid and borderline, reach only about a fifth to a quarter.

• Psychotic disorder is roughly ten times more prevalent in British prisoners than in adults in the community (Brugha and colleagues).

• About 39% of people detained in police custody in England have a mental health problem (National Institute for Health and Care Excellence guideline NG66, 2017).

Violence and homicide

• Severe mental illness raises the relative risk of violence compared with the general population, but most patients are never violent and other factors add to the risk.

• Schizophrenia is found in about one in twenty homicide perpetrators, a small and stable minority above community prevalence.

• Perpetrators with schizophrenia are mostly men, their victims are mostly known to them, and about 30% were never in contact with services.

Other disorders and offending

• Dual diagnosis does not always carry more risk than either condition alone.

• Negative symptoms and disorganisation do not automatically protect against offending.

• Command hallucinations need assessment of content, the power given to the voice, previous compliance and ability to resist, because no simple pair of features predicts compliance.

• Ictal aggression is brief, poorly directed and comes with impaired awareness, and postictal psychosis may emerge after a lucid interval.

• Suggestibility, compliance and acquiescence can shape a suspect's account, particularly with intellectual disability, but they are not universal features of autism.

• An appropriate adult under the Police and Criminal Evidence Act (PACE) follows the assessed vulnerability.

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Antisocial personality disorder and psychopathy

Development

• Conduct disorder is the childhood antecedent of antisocial personality disorder, and early, childhood onset of conduct problems is the feature most tied to progression.

• Roughly half of children with conduct disorder are later diagnosed with antisocial personality disorder.

• Shoplifting, a covert non-confrontational theft, is the commonest offence bringing young people with conduct disorder to forensic attention.

• Antisocial behaviour and conduct disorder share one heritable externalising genetic factor with alcohol and drug dependence, while anxiety and depression lie outside it.

Classification

• Dissociality describes disregard for others' rights and feelings, with self-centredness, exploitation and limited empathy; disinhibition is a separate domain.

• The older dissocial personality disorder label describes a clinical pattern; ICD-11 records the person's severity and prominent traits rather than retaining it as a category.

• A dissocial pattern centres on disregard for others; affective and relational instability point towards a borderline pattern, although features can overlap.

• The ICD-11 borderline pattern qualifier requires at least five of nine features, which include frantic abandonment avoidance and chronic emptiness.

• Explaining an offence by antisocial personality disorder is circular, because its criteria already include antisocial behaviour.

Psychopathy

• Psychopathy is related to antisocial personality disorder but distinct from it, and is measured by the Hare Psychopathy Checklist-Revised (PCL-R).

• The PCL-R rates interpersonal, affective, lifestyle and antisocial features, with a conventional cut-off of 30 out of 40 and 25 in some European work.

• A high PCL-R score does not identify the cause of an offence, and the antisocial and lifestyle features often do most of the work in predicting recidivism.

Other offender groups

Paraphilic disorders

• Paraphilic disorders are persistent, intense atypical arousal patterns, diagnosed only when acted on with a non-consenting person or when they cause marked distress or impairment.

• The interest alone is not a disorder; ICD-11 distinguishes arousal patterns from disorders and are far commoner in men.

• Paraphilic interests are typically ego-syntonic, so people seldom seek help themselves and come through external pressure, unlike the ego-dystonic experience of sexual dysfunction.

• ICD-11 places harmful or distressing arousal involving no other person, with significant risk of injury or death, under paraphilic disorder involving solitary behaviour or consenting individuals.

• Voyeuristic disorder requires a sustained, intense arousal pattern involving unsuspecting people, acted upon or causing marked distress; common adolescent sexual curiosity is not sufficient.

• Cross-dressing alone is not a disorder. A solitary or consensual arousal pattern meets ICD-11 paraphilic disorder requirements only with marked distress beyond rejection, or significant risk of injury or death; gender incongruence is assessed separately.

• Aversion therapy, used historically, was a behavioural treatment based on classical conditioning that paired an arousing stimulus with an aversive one.

Indecent exposure

• Most people convicted do not reoffend: about 20% are reconvicted after a first conviction, and those who do carry a poor prognosis.

• Arrest, court appearance and sentence deter most first-time exposers; assessment instruments only measure risk, and drug treatment is not indicated for a first non-contact offence.

• Late onset of exposing is the only protective feature, while early entrenchment, varied victim ages, alcohol misuse and previous convictions predict reoffending.

Impulse control disorders

• Kleptomania differs from hoarding disorder, which rests on distress at parting with possessions.

• Pyromania differs from the purposeful arson of dissocial personality disorder.