By Reuters Staff
Source: Reuters - 15/7/2019
Nicotine restores dynamic intrinsic brain activity in the left dorsolateral prefrontal cortex (DLPFC) of people with schizophrenia, researchers from China have found.
Schizophrenia-nicotine-dependence comorbidity is "complicated and multifactorial," Dr. Siqi Yang of the University of Electronic Science and Technology of China, in Chengdu, and colleagues write in Schizophrenia Research, online June 22.
Two leading theories have been proposed: the self-medication hypothesis, which argues that smoking helps patients relieve negative and cognitive symptoms, and the addiction-vulnerability hypothesis, which proposes that individuals with schizophrenia overvalue "drug-like rewards" while discounting negative consequences.
Multimodal-imaging studies are providing growing evidence that schizophrenia-nicotine-dependence comorbidity is neurobiologically based, the authors add, but most research has focused on static intrinsic activity and connectivity rather than dynamic intrinsic brain activity.
To investigate, the authors used the new "dynamic amplitude of low-frequency fluctuation" (dALFF) method to measure the temporal variability of brain activity in four groups: 22 smokers with schizophrenia, 27 non-smokers with schizophrenia, 22 healthy-control smokers and 21 healthy-control non-smokers.
The main effect of schizophrenia diagnosis was located in the left superior parietal gyrus (SPG), but there were no main effects for smoking. The coefficient of variation (CV) of dALFF was increased in non-smokers with schizophrenia compared to healthy non-smokers, and in smokers with schizophrenia versus healthy-control smokers.
SPG dALFF correlated positively with disease duration.
Disease and smoking had significant interaction in the left DLPFC, they team found, "which was consistent with the self-medication hypothesis."
Smokers with schizophrenia had increased CV of dALFF compared with non-smokers with schizophrenia, but there were no differences between smoking and non-smoking controls. The "study has demonstrated for the first time that nicotine restores dynamic intrinsic brain activity in the left DLPFC in patients with schizophrenia," the researchers conclude.
"This interaction may be a clinical neuromarker for increased comorbid smoking in schizophrenia."
The authors note that they did not assess smokers' oral nicotine dosage. "Further work on this topic would benefit from a controlled measure of nicotine concentration, e.g. derived from a blood sample at the time of the scan," they write. "In future work, the effect of nicotine on a non-smoking control group should also be investigated."
Schizophr Res 2019.