Insulin as a substance of misuse in a patient with insulin dependent diabetes mellitus

The relation between substance misuse and poor compliance with treatment is well established in both general medicine and psychiatry.¹,² Although young patients with insulin dependent diabetes mellitus may have lower rates of comorbid substance misuse,³ there is direct evidence that their compliance with treatment is poor.⁴ Patients with insulin dependent diabetes mellitus have an increased risk of developing a psychiatric disorder, particularly in the early course of their illness,³ and treating the psychiatric disorder improves glycaemic control.⁵

Hypoglycaemic events are common in people with insulin dependent diabetes mellitus⁶ and may be associated with cognitive, affective, and sometimes life threatening sequelae.⁷ Specific mood changes caused by changes in blood glucose concentrations are idiosyncratic, and although negative affective states are the most common, positive changes such as giddiness and euphoria are also seen.⁸ Although there is a strong relation between severe hypoglycaemia and tight glycaemic control,⁹ cases of deliberate misuse of insulin have been reported. Typically, these patients either attempt suicide or feign illness.¹⁰ We report the rare case of a patient with insulin dependent diabetes mellitus and no history of a psychiatric disorder who misused insulin regularly over a two year period for its euphoric effects. The consequences were ultimately serious.

Case report

A 30 year old man with insulin dependent diabetes mellitus was admitted to hospital. He had lost consciousness for two hours as a result of severe hypoglycaemia, and had then experienced prolonged confusion. The man, a college lecturer, was unmarried. Since his diagnosis three years previously, his diabetic control had been erratic (HbA_lc values ranged from 8% to 9.5%; normal range 2.7%-4.9%). He had had several episodes of severe hypoglycaemia, most of which had been managed at home. The patient's insulin treatment regimen consisted of a basal bolus dose of intermediate acting insulin at night and rapid acting insulin three times daily before meals.

The hypoglycaemic episode preceding the patient's admission to hospital was unexplained in terms of lifestyle or concomitant physical disease, and there was no evidence of microvascular disease. His HbA_1c value at admission was 10.1%, indicating poor recent glycaemic control, and he had failed to keep two outpatient appointments.

The man remained confused for more than three days after hospital admission. Although computed tomograms of the brain were normal and electroencephalographic findings were inconclusive, formal cognitive assessment one month later showed impaired intellectual functioning and memory functioning (performance IQ=71 and general memory index=69 on the revised Wechsler memory scale) in someone whose premorbid intelligence had been average (measured on national adult reading test). The patient had no insight into his cognitive dysfunction, but he complied with the recommendation of the psychologist that he should retire from work on health grounds.

Three months later the man was admitted to a psychiatric hospital because of depressed mood and ideas of self harm and was observed to have mood swings and irritability. He had no psychiatric history, although a collateral history from his family suggested an emotionally immature premorbid personality. Repeat cognitive assessment showed some improvement in his memory function (general memory index=92), and his mood stabilised with antidepressant medication.

At this time he recounted his difficulties in coming to terms with the diagnosis of diabetes, his erratic glycaemic control, and his serendipitous discovery of the potential mood altering effects of hypoglycaemia. He confessed that he had been dosing himself secretly with soluble insulin (three 36 U vials) every two weeks over the previous two years to induce hypoglycaemia. He described a craving for the affective state it induced: “happy ... disorientated ... like when you're drunk ... being unable to perceive things as they really were ... feeling helpless.”

The patient had no history of substance misuse and drank 8-10 units of alcohol a week. He sought no attention after these episodes of hypoglycaemia, and he prevented coma by having carbohydrate enriched drinks to hand. He clearly differentiated these episodes from the index episode described above which required hospital admission and which, he said, was a suicide attempt. This involved a larger dose of insulin (more than 200 U) and resulted in the coma and cognitive impairment described. Since the disclosure of insulin misuse the patient's medication has been supervised, and although his mood has improved considerably, his prognosis remains uncertain.

Discussion

Misuse of prescribed drugs is well described¹¹,¹² and is not confined to drugs with the potential to create dependency.¹³,¹⁴ To our knowledge, only four cases of misusing insulin to promote positive affective change have been reported. This is surprising, given the prevalence of both insulin dependent diabetes mellitus and substance misuse. Three of these cases involved people who were not diabetic but injected insulin to “get a kick,”¹⁵ to feel “quite different,”¹⁶ and for the “exquisite pleasure” associated with the perceived risk of death.¹⁷ There is only one previous report of insulin misuse in a patient with insulin dependent diabetes mellitus.¹⁸ That report described a male adolescent with a borderline personality disorder who compulsively sought the excitement and euphoria associated with a rapid lowering of his blood glucose concentration.

In our patient, regular insulin misuse over two years went unrecognised until his psychological distress culminated in a serious suicide attempt and a depressive illness. The consequences of this misuse were serious—a decline in cognitive function led to retirement from work. We alert doctors to the possibility of insulin as a substance of misuse in patients with insulin dependent diabetes and poor control, and recommend psychological evaluation where this is suspected.

Doctors should be alert to the possibility of insulin misuse, and should consider psychological evaluation, in an insulin dependent diabetic patient with poor control