Suicidal and aggressive behaviour in mental disorders: risk assessment and therapeutic management

01Suicidal behaviour

Suicide is death from an act a person carried out to end their own life. Around it lie commoner behaviours that overlap with it:

Self-harm is many times commoner than suicide, and most of it never reaches a hospital, yet it is the strongest single risk factor for suicide.

How common it is

from suicide worldwide, in 2021

720,000deaths a yearfrom suicide worldwide, in 2021

the EU's age-standardised suicide rate in 2023

10.4per 100,000the EU's age-standardised suicide rate in 2023

in the EU are men

3 in 4suicidesin the EU are men

seen in hospital after self-harm die by suicide within five years

1 in 25peopleseen in hospital after self-harm die by suicide within five years

In 2023 the EU recorded 48,370 suicides, about 1 in 100 deaths; the rate has fallen from 12.2 per 100,000 a decade earlier. It ranges from 18.8 in Lithuania, then Slovenia and Hungary, to 3.5 in Cyprus, with Greece and Malta also low, and recording practices explain part of the gap. Suicide is the second commonest cause of death at 15 to 29 in the EU, after accidents, and three quarters of the world's suicides happen in low- and middle-income countries.

After hospital-treated self-harm, about 1 in 6 people harm themselves again within a year and about 1 in 60 die by suicide within a year, the risk highest in the first weeks.

Mental disorders and suicide

Studies that reconstruct the lives of people who died by suicide find a mental disorder in about 9 in 10 in Europe and North America, fewer in Asia, and many had seen a doctor in the month before. Risk is higher when disorders coexist, especially with substance misuse. The lifetime figures below are old, often quoted estimates; a Danish register study that followed people from their first hospital contact found about 4 to 8 per cent in mood disorders and schizophrenia, highest in men with bipolar disorder.

In a stress–diathesis model, a lasting vulnerability (genes, early adversity, impulsivity, hopelessness) meets a stressor such as a loss or a relapse. Low serotonin function was an early and much-repeated biological finding, reported in Stockholm in 1976 in people who had made violent attempts (neurobiology).

Risk and protective factors

Protective factors weigh against them: close relationships and responsibility for children (especially in women), reasons for living and plans for the future, religious or moral objections, problem-solving and the ability to ask for help, engagement with a trusted clinician, and no access to lethal means.

02Assessing suicide risk

Every patient with a mental disorder is asked about suicidal thoughts, as are medical patients after a loss, a serious diagnosis or self-harm. It is a conversation in private, part of the psychiatric interview, moving from the general to the specific; family, the GP and records add what the patient cannot or will not say.

After self-harm

1. 1

   Treat the body

   The injury or poisoning is treated first, with the timing and amount of every substance taken. A paracetamol overdose can look harmless for a day and needs a timed level and treatment by protocol (paracetamol poisoning). A patient who refuses treatment has their capacity assessed.
2. 2

   Assess early

   A mental health professional sees the patient as soon as they are alert enough to take part, without waiting for medical treatment to finish.
3. 3

   Understand the act

   What happened, why and with what intent, how the person feels about it now, and what was going on in their life.
4. 4

   Formulate and plan

   What drives the risk, what makes it worse or better, and what happens next, agreed with the patient and shared with the GP and the team that follows them up.

It goes on to the mental state, past self-harm, mental disorders and substance use, whether the precipitant has passed, relationships, work, money and the law, strengths and supports, and any risk to others, such as children at home.

Why risk scales are not used to predict

Suicide is rare even among high-risk patients, while its risk factors are common, so a scale that adds them up flags many who will never die by suicide and misses many who will. In a meta-analysis, 5.5 per cent of psychiatric patients rated high risk died by suicide over about five years, against 0.9 per cent of those rated lower, but nearly half of the suicides came from the lower-risk group. A low-risk label can withhold care that is needed; a high-risk label can bring restriction that is not.

UK guidance since 2022 therefore says that risk assessment tools and scales, and global ratings of low, medium or high risk, are not to be used to predict suicide or repetition, or to decide who is offered treatment or discharged. The assessment focuses on the person's needs and safety, with a risk formulation every time. Scales such as item 9 of the PHQ-9 can structure questions or follow change, but they do not decide care.

03Managing suicide risk

Safety first

A patient with active suicidal intent is not left alone, and the means are removed. Admission is considered when the person cannot be kept safe at home or a serious disorder such as psychotic depression needs treatment; it is offered voluntarily first, with compulsory admission when they refuse and the legal criteria are met. Admission does not remove risk: wards remove ligature points, set observation from checks every 15 minutes to a nurse within arm's length, and watch for patients leaving.

The safety plan

A safety plan is written with the patient, kept by them and shared, with consent, with family and the team. A plan of this kind, with telephone follow-up after an emergency visit, cut the odds of suicidal behaviour by almost half over six months in a large study in US veterans' emergency departments.

1. 1

   Warning signs

   The thoughts, feelings, situations and behaviours that come before a crisis.
2. 2

   Coping alone

   What the person can do by themselves to get through the urge: distraction, calming, getting to a safe place.
3. 3

   People and places

   People and social settings that take the mind off it, and family or friends who can be asked for help.
4. 4

   Professional help

   The numbers of the mental health team, out-of-hours and crisis services, and emergency services.
5. 5

   A safe environment

   Removing or locking away the means, agreed with the person and, where they consent, the family.

Restricting the means

Restricting lethal means is among the best-proven ways to prevent suicide, because many suicidal crises are brief and many people do not switch methods. Smaller packs of paracetamol in the UK since 1998 were followed by 43 per cent fewer paracetamol deaths over 11 years; bans on toxic pesticides, fewer guns at home, barriers at bridges and, historically, detoxified domestic gas worked too. For the patient this means weekly supplies of dangerous medicines, avoiding the most toxic (tricyclic antidepressants, opioids), and asking family to hold medicines or remove guns.

Treating the disorder and the person

• The underlying disorder is treated: depression, psychosis, substance misuse. Lithium lowers suicide in mood disorders and clozapine lowers suicidal behaviour in schizophrenia. Antidepressants can raise suicidal thoughts in the first weeks in people under 25, so young patients are seen often early on.
• A structured, CBT-informed psychological intervention made for people who self-harm, such as CBT or problem-solving therapy, typically over 4 to 10 sessions, is offered to adults; dialectical behaviour therapy suits repeated self-harm with emotional instability.
• No drug is given as a specific treatment to reduce self-harm.
• Social problems are tackled, from debt and housing to relationships and abuse.

Follow-up

The risk is highest in the weeks after self-harm and after discharge from a psychiatric ward, and above all in the first week. Under UK guidance, people who have self-harmed and about whom there are concerns are seen within 48 hours of the assessment, and in England patients leaving a psychiatric ward are contacted within 72 hours. Appointments are made before the person leaves, and missed ones are followed up.

04Aggressive behaviour

Most people with a mental illness are never violent, and they are far more often victims than perpetrators. Severe mental illness does raise the risk: in Sweden about 1 in 20 violent crimes was committed by people with a severe mental illness. Schizophrenia without substance misuse doubles the odds of violence, and with it raises them about ninefold, so most of the excess comes from drugs and alcohol. The victims are most often family, carers and staff.

Risk factors

Acute aggression has organic causes that must not be missed: delirium, intoxication with alcohol or stimulants, withdrawal from alcohol or benzodiazepines, dementia, head injury, hypoglycaemia, hypoxia. New aggression in someone never aggressive before needs an organic cause ruled out, above all in an older or physically ill patient.

05Assessing the risk of violence

Unstructured judgement is unreliable, and actuarial scales of fixed historical factors cannot show what to change. Structured professional judgement sits between them: the clinician rates a fixed list of evidence-based factors, then judges what risk, to whom, when and in what circumstances, and plans how to manage it.

The HCR-20, in its third version, is the most widely used tool, in forensic and general settings across Europe:

The ratings lead to a formulation, risk scenarios (what could happen if things went as before, better or worse) and a plan. On wards, short daily checklists such as the Brøset Violence Checklist (confusion, irritability, boisterousness, verbal and physical threats, attacking objects) help staff act before an incident.

Violence may be close when there are threats and a raised voice, pacing, staring, clenched fists, invading personal space, or the patient says they feel threatened or out of control. Such a patient is seen in a room with an alarm and a clear exit for both, with colleagues aware; a weapon or a hostage is a matter for the police.

06Managing aggression

Aggression is managed in steps, using the least restrictive measure that will work and moving up only when it has failed.

1. 1

   Prevention

   Enough staff, activity and privacy; care plans that know the patient's triggers; listening to grievances; treating illness, pain and withdrawal.
2. 2

   De-escalation

   One member of staff leads, calmly, at a safe distance, acknowledging the anger, offering choices, a drink or a quiet room, without threats or argument; others stay close but out of sight.
3. 3

   Oral medication

   Offered as part of de-escalation: a benzodiazepine such as lorazepam, or, in psychosis, an antipsychotic the patient knows, or promethazine.
4. 4

   Rapid tranquillisation

   Medication by injection, usually intramuscular, when oral medication has been refused or has failed and urgent sedation is needed. The aim is calm, not sleep.
5. 5

   Restraint and seclusion

   Only by trained staff, as a last resort, for the shortest time.
6. 6

   Afterwards

   Physical monitoring, a debrief for patient and staff, and a review of the care plan.

Rapid tranquillisation

UK guidance makes the first two rows the first choices; if lorazepam partly works a second dose is considered, and if it fails, haloperidol with promethazine. A dose is repeated only after the first has been reviewed, at 30 to 60 minutes, within the daily maximum counting oral doses. Haloperidol is not given intravenously for this.

After rapid tranquillisation the pulse, blood pressure, respiratory rate, temperature, hydration and level of consciousness are checked at least every hour until there are no concerns, and every 15 minutes if the maximum dose was exceeded, or the patient is asleep or sedated, intoxicated, physically ill or was harmed during restraint. Deaths have happened during rapid tranquillisation and restraint.

Restraint and seclusion

Manual restraint by trained staff is used only to prevent serious harm or to give urgent medication. One person leads and protects the head and neck, and the airway and breathing are watched throughout. No pressure is put on the neck, chest or abdomen, and the prone position is avoided or kept brief, because restraint has caused deaths from positional asphyxia, more so in obesity, stimulant intoxication and after rapid tranquillisation. UK guidance advises against routine restraint for more than 10 minutes. Seclusion, supervised confinement alone in a room, is kept for detained patients who are a severe danger to others, with regular review.

Practice differs across Europe: mechanical restraint with belts is still widely used in continental Europe, in Germany, Switzerland, Denmark and Norway among others, but not in general UK practice, and Iceland gave it up decades ago. In Germany, since a 2018 ruling of the Federal Constitutional Court, five- or seven-point fixation for more than about half an hour needs a judge's approval and one-to-one supervision.

07The law in brief

European countries have mental health laws that allow a person with a mental disorder to be admitted and treated against their will under strict conditions; the details differ from country to country:

• The usual criteria are a mental disorder, a risk to the person's health or safety or to others, treatment that cannot be given less restrictively and, in some countries, impaired capacity.
• An independent body reviews the decision: a court in much of Europe (in France a judge, within 12 days), a tribunal in the UK.
• Article 5 of the European Convention on Human Rights protects liberty, and the UN Convention on the Rights of Persons with Disabilities presses for less coercion.
• In an emergency, a doctor may act to prevent immediate serious harm under the doctrine of necessity (common law in the UK), and confidentiality can be broken to protect others from serious harm.

In England and Wales, detention is under the Mental Health Act 1983. The Mental Health Act 2025 reforms it, but its changes are being brought in over about ten years and most were not yet in force in 2026. The main sections are section 2 (assessment, up to 28 days), section 3 (treatment, up to 6 months, renewable), section 5(2) (holding a voluntary inpatient for up to 72 hours) and section 136 (police removal to a place of safety). The Mental Capacity Act 2005 covers other decisions; Scotland and Northern Ireland have their own laws.