For self harm here the definition comes from NICE guidance.
https://www.nice.org.uk/guidance/qs34
> The term self‑harm is used in this quality standard to refer to any act of self‑poisoning or self‑injury carried out by a person, irrespective of their motivation. This commonly involves self‑poisoning with medication or self‑injury by cutting. Self‑harm is not used to refer to harm arising from overeating, body piercing, body tattooing, excessive consumption of alcohol or recreational drugs, starvation arising from anorexia nervosa or accidental harm to oneself.
This definition excludes drug use, but that would be covered elsewhere. For example, the front page of NCISH (National Confidential Inquiry into Suicide and Self Harm, previously NCIS and Homicide by MH patients) has this (under "improving safety in mental health services"): https://sites.manchester.ac.uk/ncish/
> Reducing alcohol and drug misuse
> We recommend there are drug and alcohol services available that work closely with mental health services for patients with mental illness and alcohol and drug misuse.
> Our evidence
> Only a minority of patients who died by suicide between 2006 and 2016 were in contact with specialist substance misuse services, despite alcohol and drug misuse being a common antecedent of patient suicide in all UK countries. In England, there was a 25% fall in rates of suicide by patients in those NHS Trusts which had put in place a policy on the management of patients with co-morbid alcohol and drug misuse.
Guidance