Cognition unaffected by substance abuse in first-episode schizophrenia
medwireNews: Substance abuse does not seem to affect cognitive functioning in patients with their first episode of schizophrenia, suggest findings from a post-hoc analysis of the European First Episode Schizophrenia Trial (EUFEST).
"Our analysis of the largest sample of first-episode patients to date comprising 323 subjects revealed only slight differences not pointing to increased cognitive impairment in patients with persisting or previous substance abuse," say T Wobrock (Georg-August-University, Göttingen, Germany) and colleagues.
At baseline and after 6 months, there were no significant differences between the 119 patients with substance use disorder (SUD) and the 204 without SUD with regard to Positive and Negative Syndrome Scale (PANSS) scores.
In terms of cognition, patients with and without SUD showed a similar performance at baseline. There was only a nonsignificant trend for an increased forgetting of initially learned words on the Rey Auditory Verbal Learning Test (RAVLT) in the patients with SUD, with a score of 1.3 versus 0.8 in patients without SUD.
At 6 months, patients with SUD were significantly faster on the Trail Making Test (TMT)-A, with a time of 34.4 seconds versus 38.8 seconds for those without SUD, indicating increased psychomotor speed, and there was a nonsignificant trend toward a slower performance on TMT-B.
But, otherwise, the two groups did not differ with regard to other neurocognitive measures.
The researchers also note in Schizophrenia Research that cognitive performance in patients who were persistent substance abusers at follow up was similar to that of patients who stopped substance use. The only difference was that patients with persistent SUD tended to have elevated positive symptoms.
Patients with SUD onset before 16 years of age had increased PANSS scores at baseline and there was a correlation between a longer duration of cannabis use and heightened cognitive performance, reduced symptom improvement, and increased extrapyramidal motor symptoms, but only in patients with a high frequency of cannabis consumption.
Wobrock and team suggest that "substance abuse may contribute to an earlier onset of schizophrenia and induce psychotic disorder before neurocognitive impairments become more prominent assuming an interaction between neurodevelopmental and neurodegenerative processes in the etiology of schizophrenia."
They add: "Patients without SUD in our sample may have higher neurodevelopment vulnerability, and patients with SUD were prone to psychosis because of the effects of the abused substances on the dopaminergic system."
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By Lucy Piper, Senior medwireNews Reporter