Drug-related deaths and suicide in prison custody in England and Wales: 2008 to 2019

• We identified 2,714 deaths in prison custody from 2008 to 2019 in the Office for National Statistics (ONS) death registrations database, after linking with the HM Prison and Probation Service (HMPPS) Deaths in custody database; equivalent to around 226 deaths a year.

• Of the identified deaths in males and females, 677 were caused by suicide and 145 were drug-related deaths as defined using ONS National Statistics definitions; because of the small number of female deaths, the figures in this article are based on male deaths unless otherwise stated.

• Male prisoners were at an increased risk of dying by suicide compared with the general male population; the risk of male prisoners dying by suicide was 3.9 times higher than the general male population between 2008 and 2019.

• The large majority (92%) of all suicide deaths in prison custody between 2008 and 2019 were caused by hanging, strangulation and suffocation.

• The risk of male prisoners dying from drug-related causes was similar to the general male population between 2008 and 2015, but was higher than the general male population between 2016 and 2019.

• Opiates were the most common drug type mentioned on death certificates (58 mentions), with methadone being the most common form; the second most common drug type was new psychoactive substances (44 mentions), which showed a particular increase in mentions between 2015 and 2019.

If you are a journalist covering a suicide-related issue, please consider following the Samaritans' media guidelines on the reporting of suicide because of the potentially damaging consequences of irresponsible reporting.

If you are struggling to cope, please call Samaritans for free on 116 123 (UK and the Republic of Ireland) or contact other sources of support, such as those listed on the NHS help for suicidal thoughts webpage. Support is available around the clock, every day of the year, providing a safe place for you, whoever you are and however you are feeling.

Statistician’s comment

“Today’s data identifies 677 deaths by suicide in males and females between 2008 and 2019 in the prison population. The risk of death by suicide was higher amongst male prisoners than the general male population.

In addition, 145 drug-related deaths were identified. The risk of male prisoners dying from drug-related causes was similar to the general male population between 2008 and 2015 but was higher between 2016 and 2019. This coincides with an increase in the number of deaths involving new psychoactive substances (including synthetic cannabinoids found in designer drugs, such as spice).”

James Tucker, Data and Analysis for Social Care and Health Division, Office for National Statistics Follow James Tucker on Twitter @ONSJames

This article reports Experimental Statistics on deaths in prisoners, by linking Ministry of Justice (MoJ) and Office for National Statistics (ONS) data together to give additional insight into suicide and drug-related deaths in prison custody.

Currently, MoJ provides official estimates of deaths in prison custody (PDF, 491KB) in England and Wales in their safety in custody statistics, with reference to broad cause of death categories assigned prior to coroner’s inquest. These categories include “self-inflicted deaths”, defined as any death of a person who has taken their own life irrespective of intent.

The ONS holds data for all deaths registered in England and Wales. It is only possible to identify individuals that died in prison custody in these data if the death was recorded as taking place in a prison, or if this information was provided by the coroner in their inquest report. By linking the ONS death registrations database with records held by the MoJ in the HM Prison and Probation Service (HMPPS) Deaths in custody database, we were able to identify deaths occurring in prison custody, using National Statistics definitions of suicide and drug-related deaths (see Section 6: Glossary).

The analysis is based on date of death occurrence during the period 2008 and 2019, which we were able to link (see our Suicide rates in the UK QMI). Date of death occurrence was used to improve comparability with safety in custody statistics. However, registration delays mean that some deaths in prison custody may not yet be included in the ONS deaths registrations database (see Section 3: Deaths in prison custody). Therefore, the level of risk shown in this analysis is likely to be an underestimate for more recent years.

We identified a total of 2,714 deaths in prison custody from 2008 to 2019 in the Office for National Statistics (ONS) death registrations database after linking with HM Prison and Probation Service (HMPPS) Deaths in custody database (see Section 4: Data linkage). The large majority of these were male deaths (2,620 deaths) comprising 97%, compared with 94 female deaths (3%) over this period. We were unable to provide analysis for the female population because of small numbers of deaths. For the number of deaths in prison custody (male and female) by year included in this analysis, please see our accompanying dataset.

Of the total deaths in prison custody during this period, 677 (males and females) were caused by suicide and 145 were drug-related deaths. Because of the overlap in our definitions (see Section 6: Glossary), 18 of the 145 drug-related deaths are also counted within the definition of suicide. Most other deaths fell into the categories of diseases of the circulatory system (International Classification of Diseases (ICD-10) codes I00 to I99; 613 deaths) and neoplasms (ICD-10 codes C00 to D48; 584 deaths). A full breakdown of cause of death by ICD chapter can be found in our accompanying dataset.

This analysis should not be seen to indicate that the risk of suicide or drug-related death changes specifically because of an individual being in prison custody. However, previous research published in 2021 on Risk factors for suicide in prisons: a systematic review and meta-analysis has shown that aspects of the prison experience may contribute to a higher risk. In addition, some risk factors that are over-represented in individuals who enter into the prison population (for example, a history of mental health problems or substance misuse) are not accounted for in this analysis but are likely to contribute to the increased risk of suicide and drug-related deaths. For more information, see Fazel and Danesh's 2002 article on Serious mental disorder in 23000 prisoners: a systematic review of 62 surveys.

Suicide deaths in prison custody

Of the 677 deaths caused by suicide in prison custody between 2008 to 2019, the large majority were male deaths, accounting for 97% (657 deaths) compared with 20 female deaths. This equates to approximately 56 deaths caused by suicide each year.

The risk of suicide was 3.9 times higher between 2008 and 2019 in the male prison population, compared with the general male population, with a particular increase in risk between 2012 and 2018 (see Figure 1). These findings are similar to those previously published by the Ministry of Justice (MoJ), showing elevated levels of risk among the prison population for self-inflicted deaths during the same period (PDF, 507KB).

Figure 1: Male prisoners are at a significantly higher risk of dying by suicide compared with the general population

Suicide death occurrences in prison custody in 2008 to 2019, standardised mortality ratios, males, England and Wales

Notes:

1. Estimates for 2017 to 2019 are expected to be an underestimate and should be interpreted with caution.
2. Figures are based on the National Statistics definition of suicide for the year the death occurred. Figures are for males aged 15 years and over.
3. The standard mortality ratio (SMR) is a common measure of mortality. The dashed line represents the level of suicide among the general male population in England and Wales (SMR equals 100). When the value of the SMR per period is above 100, the risk of suicide is higher in the male prison population compared with peers of the same age group and sex in the population.
4. Error bars show the upper and lower confidence limits, which is a margin of error around the SMR estimates. When the range of the upper and lower confidence intervals exclude 100, the risk of suicide for a given period is statistically different to that observed in the general male population of England and Wales.

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The rate of suicide, demonstrating the general trend over time, also remained statistically significantly higher in the male prison population compared with males in the general population during this period. The rate most notably increased in 2012, with a further increase between 2016 and 2018 (see Figure 2).

Suicide method

The most common method of suicide among the prison population (males and females), was by hanging, strangulation and suffocation, which accounted for 92% (624 deaths) of all suicide deaths between 2008 and 2019. In the general population, the proportion of suicides caused by this method during the same period was 54%.

Deaths caused by sharp object accounted for 4% (24 deaths) of all suicide deaths in the prison population; the proportion in the general population was 3% for the same period.

Drug-related deaths in prison custody

Of the total drug-related deaths in prison custody between 2008 to 2019 (145 deaths), 92% were male (134 deaths) compared with 11 female deaths. This equates to 12 drug-related deaths in prison custody each year.

The risk of dying by drug poisoning in the male prison population was similar to that of the general male population in England and Wales, as shown in Figure 3, between 2008 and 2015. After 2015, the rates of individuals dying by drug poisoning is higher for male prisoners than the general male population (see Figure 4).

Figure 3: The risk of drug-related deaths in the male prison population is higher than in the male general population

Drug-related death occurences in prison custody in 2008 to 2019, standardised mortality ratios, males, England and Wales

Notes:

1. Estimates for 2017 to 2019 are expected to be an underestimate and should be interpreted with caution.
2. Figures are based on the National Statistics definition of drug-related deaths for the year the death occurred. Figures are for males aged 15 years and over.
3. The standard mortality ratio (SMR) is a common measure of mortality. The dashed line represents the level of drug-related deaths among the general male population in England and Wales (SMR equals 100). When the value of the SMR per period is above 100, the risk of drug-related death is higher in the male prison population compared with peers of the same age group and sex in the population.
4. Error bars show the upper and lower confidence limits, which is a margin of error around the SMR estimates. When the range of the upper and lower confidence intervals exclude 100, the risk of drug-related death for a given period is statistically different to that observed in the general male population of England and Wales.

Download the data

.xlsx

Drug-related deaths by substance

Table 1 provides the number of times a substance was mentioned on the death certificate, with or without mentions of other drugs. Therefore, there are more mentions of drugs (184 mentions) than the overall number of individual deaths from drug poisoning (145 deaths) for males and females. These figures show the number of mentions of a substance on the death certificate; this does not necessarily indicate that the substance contributed to the final cause of death and the additive effect of combining substances should be considered.

Between 2008 and 2019, opiates were the most common substance mentioned (58 mentions) in the prison population, with methadone (36 mentions) being the most common form (Table 1). Opiates were also the most common substance mentioned in drug-related deaths in the general population during this entire period.

New psychoactive substances (NPS), referred to as psychoactive substances in HMPPS data, were the second-most common substance type (44 mentions) in prison custody; where synthetic cannabinoids (found in designer drugs, such as spice; 40 mentions) were the most common form. This differs from the general population, in which mentions of NPS occurred in 2% of drug-related deaths between 2008 and 2019. An increase in mentions of NPS were particularly notable between 2015 and 2019, in line with the increase in overall drug-related deaths in prison custody. A more detailed breakdown of Table 1 can be found in our accompanying dataset.

Comparing the cause of death recorded by HM Prison and Probation Service (HMPPS) with the Office for National Statistics (ONS) definitions of suicide and drug-related deaths

The system used by the MoJ for recording deaths in prison provides a classification for administrative and statistical purposes. Where necessary, this is amended when the final underlying cause of death has been determined by the coroner at the inquest. The ONS receives information on deaths when they are registered after a coroner’s inquest, which are then coded using the International Classification of Diseases (ICD-10) (see Section 7: Data sources and quality).

In the linked data, 843 deaths were classified as self-inflicted deaths by HMPPS; most of these deaths (673 deaths, or 80%) were included in the definition of suicide (see Table 2).

Out of 843 self-inflicted deaths, 34 were classified as drug-related deaths using the definition; this figure includes 18 deaths that are counted in the ONS’s definition of suicide (see Section 6: Glossary), because of the overlap in definitions. The majority of the remaining HMPPS self-inflicted deaths were classified by the ONS as accidental hanging and strangulation (88 out of the remaining 136 deaths).

Table 2 shows that following the coroner’s inquest conclusion, an additional four deaths are classified in the definition of suicide that were previously classified by HMPPS as having non-self-inflicted causes. The MoJ’s published death in custody statistics are reviewed and updated as new information comes from inquests.

For drug-related deaths (145 deaths), the majority of these (68%) were classified by HMPPS in the group of “other: non-natural”. Of drug-related deaths, 23% were classified as self-inflicted in prison at the time of death.

Drug-related deaths are not specifically recorded by HMPPS as a cause of death. Instead, the death will be assigned to one of the HMPPS broad causes, depending on the evidence that was available at the time of death (for example, a note suggesting that it was self-inflicted).

Registration delays

Deaths in prison custody are subject to police investigation and coroner’s inquest. In the context of prison deaths caused by suicide or drugs, a jury may be involved. Therefore, the investigation of prison deaths can take additional time to establish the cause of death.

The median registration delay for suicide deaths in the prison population between 2008 and 2019 was 595 days, compared with 155 days for the general population.

Similarly, the registration delay for drug-related deaths was 667 days in the prison population, compared with 173 days in the general population during 2008 to 2019. Given these registration delays, it is likely that these findings underestimate the level of risk particularly in the most recent years.

In this article we identified those who had died in prison custody by confidentially linking records in the Office for National Statistics (ONS) death registrations database with records held by the Ministry of Justice (MoJ). The data were processed securely, and linkage was approved by the National Statistician’s Data Ethics Advisory Committee.

The ONS was provided with a record-level extract of deaths from the HM Prison and Probation Service (HMPPS) Deaths in custody database for all deaths that occurred in prison custody from 2008 to 2020, inclusive. The extract contained a total of 3,224 individual records and included unique identifiers (for example, names and date of birth), the date of death and the cause of death category assigned to each death (see Section 7: Data sources and quality).

Pre-processing

Before linkage, both datasets (ONS death registrations and HMPPS deaths) underwent a basic normalisation process, to achieve consistency. For example, all text was converted to lower case, and we removed accents, punctuation and multiple spaces.

The linkage

We linked the two datasets using available unique identifiers (for example, forename, surname, date of birth and date of death). The linkage process consisted of direct and approximate join types.

Direct

We matched like-for-like records between the two datasets. We were able to match 2,383 out of 3,224 records over 2008 to 2020 using this technique (74%).

Approximate

For the records we were unable to match directly, we used the Jaro-Winkler distance technique to ascertain similarity of records between the two datasets. This method calculates the similarity between two strings, returning a “similarity distance” between 0 and 1 (where 0 indicates no similarity between strings and 1 indicates an exact match). The minimum distance we accepted was 0.9; this high threshold was set to correct for the uncertainty being introduced by shorter forenames and surnames. We were able to match a further 546 records using this process (17% of all 3,224 records).

Linkage results

A total of 2,929 out of 3,224 records over 2008 to 2020 were successfully linked (91%), leaving 295 records we were unable to link (9%). Given the much larger proportion of non-linked records for 2020 (103 out of 295 total non-linked records, 35%), we did not include these records in the analysis. This resulted in the final linkage rate of 2,714 out of 2,906 records (93%) between 2008 and 2019.

Most non-linked records between 2008 and 2019 (100 out of 192) had a date of death in the years 2018 or 2019 (see Table 3). This is likely because the ONS does not yet have the death registrations in the most recently available data at the time of analysis, because of incomplete coroner inquests affecting registration delays (see Section 3: Deaths in prison custody).

Other reasons why we were unable to link records may include a small number of inaccuracies in HMPPS deaths data, as detailed in the MoJ’s Guide to Safety in Custody Statistics (PDF, 538KB).

Age-standardised rate

The age-standardised rate is the total number of deaths per 100,000 people of an age group, used to allow comparisons between specified age groups.

Standardised mortality ratio (SMR)

SMR in this bulletin refers to the ratio of expected mortality risk for a population, given age-specific mortality rates from a reference population.

Deaths caused by suicide

The definition of suicide used in this article includes all deaths from intentional self-harm for persons aged 10 years and over, and deaths where the intent was undetermined for those aged 15 years and over.

Deaths related to drug poisoning

Drug poisoning deaths involve a broad spectrum of substances. As well as deaths from drug abuse and dependence, figures also include accidents and suicide involving drug poisonings as well as complications of drug use. They do not include other adverse effects of drugs (for example, anaphylactic shock), or accidents caused by an individual being under the influence of drugs. Further information can be found in our Deaths related to drug poisoning in England and Wales bulletin.

There is an overlap between the National Statistics definitions of suicides and drug-related deaths, whereby deaths caused by intentional self-poisoning and undetermined poisoning by drugs will be included in both suicide and drug-related analyses.

More details on the International Classification of Diseases (ICD) codes used to define deaths caused by suicide and drug poisoning, and deaths registration data, can be found in our Suicide rates in the UK QMI.

Standardised mortality ratio (SMR)

Most of the findings in this article are based on the SMR (see Section 6: Glossary). This method allows us to calculate how many suicide or drug-related deaths would be expected in the male prison population, should the overall pattern for these causes of death in the male general population be the same in the male prison population (England and Wales). The SMR is calculated by dividing the observed number of deaths (in the male prison population) by the expected number, expressed as a percentage:

SMRs were calculated according to the age bands used in prison services. An SMR higher than 100 indicates a greater risk among the male prison population for a given cause of death. Values less than 100 suggest lower than expected risk. Further information, including how the SMR is calculated, has been published by Public Health England.

Because of the small number of deaths, we report these findings using three-year rolling periods. This helps to smooth out fluctuations over time, however, the mortality rate in any given period will be influenced by those in the preceding years.

The SMR should not be used to understand how the level of risk changes over time; for this purpose, we have also included age-standardised rates. Further information on age-standardised rates can be found in our Suicide rates in the UK QMI.

Ministry of Justice (MoJ) data

Summary details of each death in prison custody are recorded in HM Prison and Probation Service (HMPPS) Deaths in custody database.

The system used for recording deaths in prison provides a classification for administrative and statistical purposes using the following four broad categories of death:

• natural causes: any death of a person because of a naturally occurring disease process

• self-inflicted: any death of a person who has apparently taken his or her own life irrespective of intent

• homicides: any death of a person at the hands of another

• other: non-natural: any death of a person that cannot be easily classified as natural causes, self-inflicted or homicide

Where there is insufficient information to assign an apparent cause, deaths are classified as “other: awaiting further information”. This is a temporary classification that is updated following the outcome of inquest, after which the classifications in all other cases are revised where necessary. Further information on the data source can be found in the MoJ’s Guide to safety in custody statistics (PDF, 537KB).

Death registrations data

All suicide deaths and most drug-related deaths are registered by coroners following the conclusion of an inquest. Following death registration, the Office for National Statistics (ONS) assigns each death with an underlying cause based on the information provided by the coroner. With this, every death is assigned a code from the International Classification of Diseases (ICD-10).

Population data

Two sources of population data were used in this analysis. To define the prison custody population at risk, we used available prison custody population data published by the MoJ.

To calculate rates in the general population of England and Wales, we used our mid-year Population estimates for the UK, England, Wales, Scotland and Northern Ireland.

Limitations of the analysis

The figures in this article have been produced as Experimental Statistics, which are in the testing phase and not yet fully developed. Official estimates of self-inflicted deaths in prisons should be taken from the MoJ’s safety in custody statistics. It should be noted that the total numbers of deaths included in this analysis are not equal to those in safety in custody statistics, because of both the linkage process and the differences in HMPPS classification and ONS definitions.

The analysis is based on deaths that occurred during the period between 2008 and 2019, which we were able to link, and excluded cases from 2020 where the proportion of non-matched cases was higher.

It is likely that these findings underestimate the level of risk because of registration delays, as the analysis is based on the date of death. This is particularly the case for the most recent period (2017 to 2019), which we flag in this article as being preliminary.

Acknowledgements

We would like to thank colleagues from the Ministry of Justice and Professor Louis Appleby for their support and valuable feedback on this work. We would also like to thank colleagues from our Analytical Data and Customer Service team, particularly Ben Aspey and Justine Pooley who worked on the data linkage for this project.