Test of the Serotonin Transporter Gene × Early Life Stress Interaction Effect on Subjective Well‐Being and Loneliness Among Japanese Young Adults

Association between internet addiction, brain structure, and social capital in adolescents

Of late, internet addiction among adolescents has become a serious problem, with increased internet use. Previous research suggests that the more people become addicted to the internet, the more they isolate themselves from society. Conversely, it has been suggested that abundant social capital (the networks of relationships among people who live and work in a particular society) protects people from becoming addicted to the internet. This study focused on the brain structure of typical adolescents (10-18 years of age) and hypothesized that the size of the left dorsolateral prefrontal cortex (DLPFC), which is thought to be associated with self-control ability, is associated with both internet addiction and social capital. Voxel-based morphometry analysis indicated that left DLPFC volume was negatively correlated with the severity of internet addiction and positively correlated with social capital. Furthermore, correlation analysis demonstrated that the severity of internet addiction and social capital were negatively correlated. The statistical association between them was no longer significant when left DLPFC volume was used as a control variable. These results suggest that the left DLPFC may mediate the relationship between social capital and internet addiction in adolescents.

Genetic architecture of well-being: cumulative effect of serotonergic polymorphisms

Serotonin influences mental health and well-being. To understand the influences of genetic variations in serotonin pathway on well-being, we examined the effects of seven serotonergic polymorphisms on subjective well-being (i.e. affective balance and global life satisfaction) and psychological well-being (i.e. optimal psychological functions in the face of existential challenges) in a larger sample. Results indicated that the cumulative genetic score, but single genetic effects of serotonergic polymorphisms, was related to individual differences in well-being. Specifically, individuals with a greater cumulative genetic score, which is related to a low risk of depression, tended to exhibit high levels of subjective well-being and psychological well-being. These findings suggest that the overall serotoninergic genetic profile, rather than a specific genetic polymorphism, could greatly influence the individual differences in well-being.

A Re-evaluation of Candidate Gene Studies for Well-Being in Light of Genome-Wide Evidence

Ever since twin-family studies found that a substantial amount (± 40%) of the variation in well-being can be explained by genetic variation, several candidate genes have been proposed explaining this variation. However, these candidate gene and candidate gene-by-environment interaction studies have been surrounded by controversy regarding the validity and replication of their results. In the present study, we review the existing candidate gene literature for well-being. First, we perform a systematic literature search that results in the inclusion of 41 studies. After describing the results of the included studies, we evaluated the included candidate polymorphisms by (1) looking up the results for the studied candidate SNPs in a large well-being genome-wide association study, (2) performing association analyses in UK biobank (UKB) data for the candidate variable number tandem repeats (VNTR) and the APOE ε4 allele, and (3) studying possible candidate interactions with positive and negative environmental moderators using UKB data. We find no support for any of the candidate genes or candidate gene-environment interactions for well-being, with the exception of two SNPs that were chosen based on genome-wide evidence. While the generalizability of our findings is limited by our phenotype and environment definitions, we strongly advise well-being researchers to abandon the candidate gene approach in the field of well-being and move toward genome-wide approaches.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10902-022-00538-x.