Research into the mental health of prisoners, digested

Around the world, more people than ever are locked up in prisons – estimated to be in excess of 11 million people, up by almost 20 per cent since the turn of the millennium (pdf).

According to a recent House of Commons Briefing Paper the rate of increase is even higher than this in the UK where prison populations are at a record high. Many of these incarcerated individuals have intensifying mental health needs – for instance, the same briefing paper reports that UK rates of self-harm in prisoners were 25 per cent higher in 2015 than in 2014.

Ahead of this week's meeting of the All Party Parliamentary Group for Psychology on the topic of Mental Health in the Criminal Justice System, here we provide a digest of research into the mental health of prisoners.

Prisoners are at much higher risk of mental health problems than the general population

According to a systematic review published in 2012, involving data from over 30,000 prisoners worldwide from 24 different countries, around 12 per cent of prisoners have a diagnosis of depression and nearly 4 per cent have a diagnosis of psychosis (compared with approximately 4 per cent and 1 per cent, respectively, in the general population). Other mental health conditions are also more common among prison populations than the general public, including substance misuse and personality disorders. The statistics show that women prisoners seem to be at especially high risk of mental health problems.

Prisoners are at elevated risk of suicide

These greater mental health vulnerabilities also manifest in much higher suicide rates among prison populations than among the general public. A study published last year analysed prison suicides across 24 countries between 2011 to 2014. This revealed a threefold increased suicide risk among male prisoners, and a ninefold increased risk of suicide among female prisoners, compared with the general population. The study also measured a number of prison factors to see if these correlated with suicide rates, such as over-crowding and the staff-prisoner ratios, but none of them did. "There are no simple ecological explanations for prison suicide," the researchers said.

An unresolved issue is whether prison causes mental health problems or people with mental health problems are more likely to go to prison

A recent review in Lancet Psychiatry described this question as a "key issue" for the field, citing in favour of the "importation" argument two studies that suggested offending rates are higher than average among people with a diagnosis of schizophrenia or depression, which could account for the elevated rates of these diagnoses among prison populations.

Meanwhile, a small British study published in 2011 found that rates of depression actually decreased, and rates of psychosis remained stable, among the prisoners they followed for two months from the beginning of their sentence. "It appears that the first 2 months of imprisonment do not have a universally detrimental impact on mental health, even among those with pre-existing mental illnesses," the researchers said (other researchers have previously suggested that the relative safety of prisons, the structure, and access to psychiatric care could be responsible for symptom improvements, and there is even research on post-traumatic growth in prison through finding meaning in the experience).

Note, however, that the pattern in the 2011 study was somewhat different for women prisoners, who did not show declines in symptoms. "The notion that women are differently and disproportionately affected by imprisonment is well supported in the literature," the researchers added. The study also showed that symptom prevalence among prisoners was highest during the first week in prison: "Our findings confirm that the first week of custody continues to represent a period of heightened distress and risk among all newly received prisoners," the researchers said.

Several pre-incarceration factors have been found to correlate with increased risk of prisoner mental health problems

While the debate continues around whether and what factors of prison increase risk of mental illness, a study published this year that assessed over 750 prisoners from two UK prisons found multiple "imported factors" that were associated with increased risk of having a mental health problem in prison (in this study, around 40 per cent the prisoners had a mental health problem).

These factors included: describing oneself a worrier; being impulsive; having difficulty getting on with others; having been a victim of sexual abuse in childhood (see also); and having learning difficulties at school. "[P]ersonality type may be one area well worth exploring when carrying out initial intake assessments and designing regime or individual sentence plans, as it appears certain dispositions may be useful predictive markers [for risk of mental health issues]," the researchers said.

Counter-intuitively, having a previous prison sentence, past substance abuse problems and being unemployed prior to prison were all associated with lower risk of mental health problems in prison (at a statistically significant level or showing a trend in that direction). "A possible explanation for this finding is that the presence of these factors may make the adoption of a prisonized identity an easier process, which in turn eases mental stress," the researchers said (for more on the processes of "prisonisation" – i.e. how prison changes people – see here).

Prisoners with mental health problems are more likely to perpetuate and be the victims of violence

A US Department of Justice report (pdf) found that prisoners with mental health problems were more likely to have been charged with physical or verbal assault and more likely to have been injured in a fight, compared with prisoners without mental health issues. Other research has highlighted how prisoners with mental health problems are more likely to be victimised: for instance, another US study found that 1 in 12 male prisoners with a mental health diagnosis reported sexual victimisation by another inmate, compared with 1 in 33 male prisoners without a mental health diagnosis. Prisoners with mental health problems are also at increased risk of physical assault by others.

There is a lack of quality research on interventions for prisoners with mental health needs

Given the high rates of mental health problems among prison populations, there is a worrying lack of large-scale intervention studies. The recent Lancet Psychiatry review of mental health issues in prisons stated that this is likely due to organisational challenges, lack of funding, and "a perceived division of prisoner health from public health in general". There is some limited evidence for beneficial effects for prisoners of programmes based around CBT, DBT (dialectical behaviour therapy) and Yoga. "But the effect sizes are not large; [it remains unclear] whether they would hold in better quality designs (e.g. using active controls and not waiting list or treatment as usual controls), and it is uncertain whether any improvements are sustained," the review states. It goes on to recommend that "More evidence is required to determine which psychological therapies are most effective for mental health problems in prison, and whether they can be provided in a group-based formats." Findings from the community may not generalise to the community, the review authors warn, because of the unique challenges in prison of "the increased structures, different rules, housing, and access to drugs".

Regarding the prison drug problem, a recent report by the HM Chief Inspector of Prisons for England and Wales warned about the "rapid increase in the availability of new psychoactive substances (new drugs such as 'Spice' and 'Black Mamba' that are developed or chosen to mimic the effects of illegal drugs such as cannabis, heroin or amphetamines and may have unpredictable and life-threatening effects)…" and it stated that these drugs have been linked with "problems such as bullying, debt and medical emergencies requiring hospitalisation".

About the author

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest