Amphetamine and methamphetamine induced psychosis: toxicological findings, comparison with acute symptoms of schizophrenia and transition of diagnoses. A clinical investigation

Abstract

Background: There is a long-standing debate about the relationship between amphetamines and psychoses. While some have found psychoses induced by amphetamines to be indistinguishable from schizophrenia, others have found that psychoses induced by amphetamines, in contrast to schizophrenia, were characterized by visual hallucinations and lack of thought disorder. It has also been discusses whether there really are sharp boundaries between the two diagnoses, and whether there is a transition between them. Also, there are few studies which investigate the relationship between blood concentrations of amphetamines and clinical presentation, and whether methamphetamine could have a greater potential for generating psychoses than amphetamine. Objectives: Our main objectives were to investigate whether there are clinically evident differences between psychosis induced by amphetamines and acute symptoms of schizophrenia, and if there is a transition from amphetamine-/methamphetamine induced psychosis to schizophrenia. We also wanted to study the relationship between blood concentrations of amphetamines and clinical presentation, and if methamphetamine was more potent in generating central nervous influence and psychosis than amphetamine. Methods: The first source of data were from two psychiatric wards at public hospitals, where blood and/or urine samples were collected as soon as possible after admission for 87 individual patients in 2003 and 285 in 2006/2007. Psychotic symptoms were assessed with the positive subscale of the Positive and Negative Symptom Scale (PANSS) for the patients admitted in 2006/2007. The second source of data came from the Norwegian Institute of Public Health (NIPH) where all blood samples from apprehended drivers in Norway are analysed. Blood samples were obtained from 735 apprehended drivers from the same time periods and the same geographical area as the acutely admitted patients. On the basis of blood drug concentrations among patients admitted to psychiatric wards and among apprehended drivers, drug influence was estimated. In 2012, we did a follow-up by reviewing their hospital records of 35 patients who were admitted to one of the two hospitals and were positives for amphetamines in 2006/2007. From these 12 individual patients received diagnoses specifically related to disorders due to psychoactive substance use (F10-F19 according to the ICD-10 classification of mental and behavioural disorders). Results: We compared positive PANSS scores for 1) patients who received a diagnosis of schizophrenia and were negatives for amphetamines in blood and/or urine with PANSS scores (N=8), to 2) patients who were positive for amphetamines in blood and/or urine and either received a diagnosis of amphetamine-induced psychosis or psychoses induced by multiple drugs (N=31). We found no differences between the two groups (total PANSS 23.5 vs 22.8, p=0.783). With rising blood levels of amphetamines no differences in symptoms, as measured by PANNS, were observed (urine positives only total PANSS 18.0, low/moderate blood concentrations 20.6, high blood concentrations 20.9, p=0.782). Having amphetamines in the blood increased the likelihood of being judged clinically to be under the influence of drugs (OR 5, 95% CI 1-17) compared to having other substances in the blood. We found that individuals who had taken methamphetamine had a 3-4 times increased risk of being admitted to an acute psychiatric ward compared to those who had taken only amphetamine (adjusted OR= 4.423 (2.031 – 9.631)). The apprehended drivers were the comparison group here. When we did the follow-up in 2012, four patients who had not been diagnosed with schizophrenia before, now had got this diagnosis, all in the period 2008–2010. Conclusions: In acute phase, i.e. at the time of admission to acute psychiatric wards, it is not possible to distinguish patients with psychoses induced by amphetamines from patients with schizophrenia. An important clinical implication is that patients with dual diagnosis may be mis-diagnosed as only having a drug-induced psychosis and may not receive the correct treatment). Also, we found no relationship between symptoms and blood concentrations of amphetamines and no strong relationship between being positive for amphetamines and being judged as under the influence of drugs by the physician on call. On the basis of our main findings, we propose a traditional stress-vulnerable model for understanding the relationship between psychosis induced by amphetamines and schizophrenia.