J Nerv Ment Dis. 2018 Aug;206(8):644-656. doi: 10.1097/NMD.0000000000000861.
The general purpose of this review is to present an updated literature overview of neurobiological/clinical aspects of Internet addiction (IA), particularly of overlaps and differences with bipolar affective disorder (BPAD). Articles with clinical/neurobiological aspects of IA or similarities/differences with BPAD as main topics, from 1990 to present and written in English language, were included. Comorbidity between IA and other psychiatric disorders, including BPAD, is common. Dysfunctions in dopaminergic pathways have been found both in IA and in mood disorders. Most of investigations in IA support a chronic hypodopaminergic dysfunctional state in brain reward circuit and an excessive reward experience during mood elevation. Neuroimaging studies show prefrontal cortex abnormalities shared between addictive and bipolar patients. BPAD and IA present numerous overlaps, such as polymorphisms in nicotinic receptors genes, anterior cingulate/prefrontal cortex abnormalities, serotonin/dopamine dysfunctions, and good response to mood stabilizers. The future is to clarify diagnostic criteria to better define the IA/BPAD relationship.