The two types of overdose identified, accidental overdose and overdose with suicidal or self-harm intent, are not often considered concurrently. However, both are large contributors to fatality amongst PEH. In England and Wales in 2021, 35% of deaths in PEH were caused by substance overdoses and 13.4% by suicide [2]. These two types of overdose are more likely to be at ends of a spectrum with considerable overlap rather than being distinct classes, with suicidal thoughts shown to be present in almost 50% of illicit NFOD [17] and suicidal ideation a risk factor for accidental overdose [18].

The mixture of illicit, over the counter, and prescription drugs reported in the NFOD most likely reflect the combination of these two types of overdoses, with paracetamol most commonly used for self-harm attempts in PEH [19], and heroin, benzodiazepines and cocaine frequent in street drug overdoses [10]. The importance of considering the type of overdose lies in the preventative approach from a health care perspective. Although sharing similarities that may benefit from comparable holistic and mental health care, there may be some variation in the approach to dealing with patients in each group. For example, ensuring naloxone for those likely to overdose on heroin vs limiting the prescribing of medicines potentially associated with overdose. Alternative approaches are in place in other UK cities with opportunities for heroin assisted treatment and supervised drug consumption in Glasgow, for example.

Alongside factors previously identified to be associated with NFOD including being female [9], a polysubstance user [9], being white [20] and known substance misuse, the most novel risk factors identified related to the association with chronic health conditions. This is already recognised from a mental health perspective, with mental health disorders shown to be the second highest risk factor for overdose behind substance use in a meta-analysis [21]. Chronic physical health conditions have not been previously considered a risk factor, but we do know there is a high level of multi-morbidity within this population, with a mean of 2.2 mental health problems and 5.4 physical health problems per person reported in a group of PEH with a recent NFOD [10].

Respiratory disease (particularly asthma), BBV (particularly Hep C) and migraines were associated with an increased risk of NFOD. While the timing of diagnosis and overdose events remains unknown, thus making the direction of these relationships unclear, chronic health conditions come with a large burden to PEH physically, mentally and socially [22].

Most overdose incidents reported here (87%) had contact with emergency services (ambulance or the emergency department), although this is likely an overestimation if considering all episodes of overdose in the community as many overdoses are likely to unrecorded where no contact with health services were made. Just over half (53%) arrived by ambulance. Self-discharge from emergency services was high, with 14% of those that attended ED self-discharging and 19% of those that had an ambulance call out refusing help. Similar reports of self-discharge from the ED have been documented [11]. Self-discharge following a poisoning episode could be associated with an increased risk of death [23]. Waiting environment, the length of time of the wait and waiting around other people in the emergency department could contribute to the self-discharge before assessment [24].