Main findings

This national consecutive-case series study revealed specific characteristics associated with different methods of suicide among people in recent contact with mental health services. Suicide by hanging/strangulation was associated with being male and younger age, depression, a short illness history and recent self-harm. Patients who died by self-poisoning were more often female, with diagnoses of drug dependence/misuse and personality disorder and previous self-harm and alcohol misuse. We also found that opioids were the most commonly used substance and in around half of cases these had been prescribed for the patient. Deaths by jumping were associated with ethnicities other than White British, schizophrenia and bipolar disorder, current in-patient status or recent discharge and non-adherence with medication. Drowning was strongly associated with older age, female patients, schizophrenia and in-patient status. Suicide by cutting/stabbing was also associated with older age and schizophrenia, and with recent service contact and a short history of illness, while deaths by gas inhalation were associated with being male.

Findings in relation to previous work

In contrast with Huisman et al,^{Reference Huisman, van Houwelingen and Kerkhof12} who reported that patients under mental health services diagnosed with a depressive disorder were less selective with methods, we found depressive disorder was only associated with suicide by hanging. Other factors associated with hanging, such as male gender and younger age, are in line with previous research,^{Reference Hunt, Swinson, Palmer, Turnbull, Cooper and While9,Reference Huisman, van Houwelingen and Kerkhof12} suggesting that these characteristics are persistent concerns for this method of suicide.

The presence of social adversity, drug and alcohol misuse and diagnoses of personality disorder in those who died by self-poisoning has previously been reported.^{Reference Hunt, Swinson, Palmer, Turnbull, Cooper and While9,Reference Huisman, van Houwelingen and Kerkhof12} With respect to the use of opioids in self-poisoning, Oquendo and Volkow^{Reference Oquendo and Volkow17} noted that populations likely to receive prescriptions for opioids may also be those at increased risk of suicide, including people with chronic pain or mood disorders. Indeed, in our study 44% of those who died using opioids also had a major comorbid physical illness, including 34% with chronic pain. NICE guidelines on management of chronic pain recommend that those with chronic pain should not be prescribed opioids because of issues around dependence and withdrawal.¹⁸

Suicide by jumping in mental health patients has previously been identified as more common among people from an ethnic minority background.^{Reference Hunt, Swinson, Palmer, Turnbull, Cooper and While9,Reference Hunt, Richards, Bhui, Ibrahim, Turnbull and Halvorsrud19} Recent research on suicide in ethnic minority patients has evidenced that some of these groups may present to services with fewer indicators of suicide risk and more rapidly changing risk, possibly because of differences in expressing mental distress.^{Reference Hunt, Richards, Bhui, Ibrahim, Turnbull and Halvorsrud19} This may lead to individuals choosing more impulsive methods of suicide, such as jumping.^{Reference Huisman, van Houwelingen and Kerkhof12} Earlier work has also highlighted an association between jumping and the presence of psychotic disorders, with suggestions that impulsivity and rapid changes in mood and cognition linked to active psychotic symptoms (e.g. delusions, hallucinations) may increase the likelihood of selecting more violent methods.^{Reference Docherty, Bakian, DiBlasi, Shabalin, Chen and Keeshin20} Importantly, ethnic minority background and a diagnosis of schizophrenia, two of the main risk factors for jumping in our study, have been found to be associated with each other.^{Reference Halvorsrud, Nazroo, Otis, Brown Hajdukova and Bhui21} This could be because of the reported inequalities experienced by ethnic minority groups in accessing mental healthcare and receiving appropriate treatment,^{Reference Das-Munshi, Bhugra and Crawford22} potentially resulting in people with serious mental illness reaching services later and being more severely ill than White patients.

Studies carried out in both general and patient populations have identified women and people aged 65 and above to be at greater risk of suicide by drowning,^{Reference Hunt, Swinson, Palmer, Turnbull, Cooper and While9,Reference Haw and Hawton23} which is consistent with our findings. In clinical groups, there is some evidence of an association between drowning and schizophrenia^{Reference Pan, Chen, Chang, Wang, Chen and Su24} and with being an in-patient.^{Reference Hunt, Swinson, Palmer, Turnbull, Cooper and While9,Reference Powell, Geddes, Deeks, Goldacre and Hawton25} The higher prevalence of drowning among in-patients has been linked to the proximity of rivers near hospitals and lack of access to other means of suicide.^{Reference Powell, Geddes, Deeks, Goldacre and Hawton25}

Research on cutting/stabbing is scarce and has mainly been examined in relation to self-harm or attempted suicide. Kimura et al^{Reference Kimura, Ikeda, Kumazaki, Yanagida and Matsunaga26} found that those who attempted suicide by self-stabbing were more often male and older compared to those who attempted suicide by jumping; however, mood disorders were more common and psychotic disorders less common. In contrast, we found those who died by cutting/stabbing were more likely to have schizophrenia, although this was in comparison with patients dying by all other methods. There is also limited evidence on gas inhalation deaths as a whole, with most research focusing on specific gases and case reports.^{Reference Burnett, Chen, McGillivray, Larsen and Torok27} Nonetheless, in a recent Canadian study, Sinyor et al^{Reference Sinyor, Williams, Vincent, Schaffer, Yip and Gunnell28} identified a heightened risk of dying by gas inhalation in males, as well as a reduced risk of being diagnosed with a psychiatric disorder.

Clinical implications

This study has identified particular patient factors associated with each of the specific methods of suicide, leading to implications for prevention in clinical practice. Clinicians should be aware of the most common methods of suicide in certain patient groups and be able to explore these when making an assessment.

The prevention of hanging is a major challenge outside of institutional settings. Our finding of higher rates of self-harm in patients who died by hanging may be indicative of escalation in method that clinical staff should be aware of. Importantly, there may be a window of opportunity for services to intervene with those who self-harm and present to the emergency department, and for whom there is an opportunity for secondary prevention through medical management.^{Reference Sabrinskas, Hamilton, Daniel and Oliffe29} In a national cohort study, Runeson et al^{Reference Runeson, Haglund, Lichtenstein and Tidemalm30} reported a high risk of future suicide among people with severe mental illness who had been admitted following a suicide attempt and that the risk was greatest for those who had self-harmed by hanging. Recently, the suicide prevention strategy for England² has emphasised the need for first responders and front-line staff to be equipped to respond to people in crisis. More generally, there may be a place for continuing to challenge perceptions of hanging as a quick, easy, painless and clean method, notably in the media.^{Reference Biddle, Donovan, Owen-Smith, Potokar, Longson and Hawton31} Indeed, such views may develop through inappropriate media reporting and providing access to technical details,^{Reference De Leo, Evans and Neulinger10,Reference Sabrinskas, Hamilton, Daniel and Oliffe29,Reference Biddle, Donovan, Owen-Smith, Potokar, Longson and Hawton31} which has led to recommendations for tighter media reporting of suicide.³²

Patients who died by self-poisoning had commonly presented to services with a range of social, behavioural and clinical issues, and may benefit from joined-up care between services. This should include support from alcohol and drug services to address the high prevalence of substance misuse in this group. Both primary and secondary care, including general practitioners (GPs), pharmacists and mental health services, should ensure appropriate and safe prescribing and close monitoring of access to medication.^{Reference Gorton, Littlewood, Lotfallah, Spreadbury, Wong and Gooding33} This may be particularly relevant for those receiving pharmacological treatment for comorbid physical conditions who are at increased risk of suicide by self-poisoning compared to those with mental illness alone.^{Reference Pitman, Tham, Hunt, Webb, Appleby and Kapur34} Specifically, mental health services should be aware of the risk associated with opioids prescribed for pain and enquire about the availability of these medications at home, especially in older patients.³⁵

Environmental control initiatives are likely to be most effective in preventing suicide by jumping and drowning in those with schizophrenia and among in-patients, because of rapid changes in mood, cognition and risk, and ease of access, respectively.^{Reference Docherty, Bakian, DiBlasi, Shabalin, Chen and Keeshin20,Reference Powell, Geddes, Deeks, Goldacre and Hawton25} While in-patient wards have become safer over time and suicide rates in in-patients have decreased,^{Reference Kapur, Ibrahim, While, Baird, Rodway and Hunt36} in the current study 68% of in-patients died off the ward, including those who died at nearby railway or river locations. Efforts around local planning and training of railway staff as recommended by NICE⁵ are likely to increase the chances of last-minute intervention and may delay impulsive actions. High-frequency locations in close proximity to hospitals and care homes should be considered in suicide prevention strategies, through joint working between clinical commissioners and local authorities.³⁷ There is now established evidence that safety measures such as barriers and fences at bridges are effective in preventing suicide.^{Reference Pirkis, Currier, Too, Bryant, Bartlett and Sinyor38}

While gas inhalation was a less common method among patients than in the general population, controlling access to acquiring toxic gases is important to prevention. Limiting access to gases may be challenging, but improving online safety may play an important part in both accessing information on and purchasing these gases.^{Reference Burnett, Chen, McGillivray, Larsen and Torok27} The Online Safety Act 2023, which was recently passed in the UK, has made positive steps in preventing platforms from posting harmful material relating to suicide and self-harm, and has made encouraging or assisting suicide online a priority offence.

In addition to method-specific recommendations, our findings support consideration of availability to means in clinical practice.^{Reference Zalsman, Hawton, Wasserman, van Heeringen, Arensman and Sarchiapone39} One approach is means-restriction counselling, which aims to educate patients and their family/carer on the risks associated with access to means; this has been found to lead to patients and/or their carers disposing of or improving safe storage of means of suicide present in the home.^{Reference Bryan, Stone and Rudd40} Stronger and up-to-date empirical evidence is needed on the effectiveness of means restriction in risk assessment and management, and its implementation in practice.^{Reference Hunter, DiVietro, Boyer, Burnham, Chenard and Rogers41}

Limitations

This was a large UK-wide study using robust case ascertainment and our findings add to the scarce literature on suicide methods among mental health patients. However, it is important to consider certain methodological limitations. First, the observational nature of the study cannot ascertain causality or the exact mechanisms in choosing a specific method. Second, our data relied on the accuracy of patient case notes and judgement from clinicians who were not blind to patient outcome. This may have introduced some bias, although most data variables are based on objective information and the quality of the NCISH methodology has been found to be reliable.^{Reference Appleby, Shaw, Amos, McDonnell, Harris and McCann42} Third, these findings are not generalisable to all individuals with mental illness as our sample only included those in contact with services in the year before death. Fourth, we did not examine less common methods of suicide, such as burning, electrocution and firearms, owing to small numbers but future research may consider investigating these. Finally, we did not investigate whether there was an effect of year on patient characteristics and suicide method. Adjusting for year may be of interest to examine changing trends in risk factors, especially when changes in method selection have been observed in the general population,^{Reference Mok, Kapur, Windfuhr, Leyland, Appleby and Platt43} and to ensure current practice is informed by recent trends. This is currently being explored in a further study by the research team.

In summary, recognition of features associated with common methods of suicide may help in the development of suicide prevention strategies by providing adequate support to mental health patients. The challenge in reducing suicide by hanging is clear but may be achieved through greater encouragement to seek help during a mental health crisis and effective treatment of depression. The complex clinical profile of those who have died by self-poisoning highlights that preventative efforts should target improved integration across primary and secondary care and dual diagnosis services, as well as safer prescribing. Environmental control initiatives such as barriers and helpline posters are likely to be most effective for those at risk of jumping or drowning. More broadly, responsible media reporting of suicide and engaging patients and their families or carers in conversations on means access and restriction may be beneficial at times of crisis.