Heroin and methamphetamine are highly psychotoxic drugs, causing structural damage to the brain and cognitive deficits. At the neural level, both heroin and methamphetamine use disorders are associated with dysfunction of the dopamine system, leading to changes in neurotransmission at the dopamine terminal of the nucleus accumbens, caudate nucleus and frontal cortex, but there are differences in neural activity of related brain structures involving cortico-striatal circuits.

Hence, there may be similarity and heterogeneity between stimulants and opioids in terms of cognitive impairment. Some drug-related behaviors, such as abstinence duration, age of first drug use, quantity of drug use, and total time of drug use, can negatively affect cognitive function. However, to date, few studies have compared patterns of cognitive impairment and the relationship between cognitive function and drug-related variables in methamphetamine and heroin patients.

A research team led by Prof. ZHANG Xiangyang from the Institute of Psychology of the Chinese Academy of Sciences, aimed to compare the similarities and heterogeneity of cognitive impairment among heroin and methamphetamine-dependent individuals, and to explore the correlation between cognitive impairment and drug use behavior.

They recruited 567 pure methamphetamine-dependent patients, 78 pure heroin-dependent patients and 201 healthy volunteers for the study. Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was used to assess cognitive function including immediate memory, visuospatial/constructional index, language, attention, delayed memory, and total scores.

The researchers found that methamphetamine and heroin patients overlapped in terms of cognitive impairment, with both having similar deficits in immediate memory, visuospatial markers, language, attention, and overall cognitive function. But in terms of delayed memory, methamphetamine-dependent patients had more impairment than heroin-dependent patients.

In addition, methamphetamine and heroin have different patterns of cognitive impairment. Specifically, cognitive impairment in methamphetamine-dependent patients accumulates with months of drug use, cognitive impairment in heroin-dependent patients was unrelated to any drug-related behavior and was more likely to be impaired directly.

The study entitled "Differences in cognitive deficits in patients with methamphetamine and heroin use disorder compared with healthy controls in a Chinese Han population" has been published on Progress in Neuro-Psychopharmacology and Biological Psychiatry on March 4.