Commentary on the Special Issue on the Adolescent Brain: Incentive-based striving and the adolescent brain

Leisure Boredom, Timing of Sexual Debut, and Co-Occurring Behaviors among South African Adolescents

Sex during adolescence is normative; however, there are substantial individual differences in the timing and context of sexual debut. Leisure boredom is an underexplored correlate of sexual behavior that is associated with many adolescent health outcomes. We investigated if and how individual differences in leisure boredom may be associated with timing of sexual debut, and whether individuals engage in safe or risky behaviors at debut. Survival analysis, logistic regression, and Poisson regression were applied to eight-wave longitudinal data obtained from 3,088 South African adolescents (baseline M_age = 13.9 years) to examine associations between leisure boredom and cumulative hazard of sexual debut across adolescence, odds of co-occurring sexual behaviors, and incidence rate of co-occurring sexual risk behaviors at debut. Higher levels of leisure boredom were associated with elevated hazard cumulatively across adolescence. Higher levels of leisure boredom were also associated with lower odds of safe sex and higher odds of substance use during sex and transactional sex at sexual debut, but not casual sex or condom non-use at sexual debut. Although odds of singular risk behaviors were lower for girls than for boys, the association between leisure boredom and the number of risk behaviors at sexual debut was stronger for girls than boys. Higher trait leisure boredom was associated with elevated hazard of sexual debut, greater likelihood that risky behaviors accompanied sexual debut, and greater number of co-occurring risky behaviors at sexual debut. Results support leisure boredom as a potential target for preventing sexual risk behavior among South African adolescents.

Pubertal maturation and sex effects on the default-mode network connectivity implicated in mood dysregulation

This study examines the effects of puberty and sex on the intrinsic functional connectivity (iFC) of brain networks, with a focus on the default-mode network (DMN). Consistently implicated in depressive disorders, the DMN's function may interact with puberty and sex in the development of these disorders, whose onsets peak in adolescence, and which show strong sex disproportionality (females > males). The main question concerns how the DMN evolves with puberty as a function of sex. These effects are expected to involve within- and between-network iFC, particularly, the salience and the central-executive networks, consistent with the Triple-Network Model. Resting-state scans of an adolescent community sample (n = 304, male/female: 157/147; mean/std age: 14.6/0.41 years), from the IMAGEN database, were analyzed using the AFNI software suite and a data reduction strategy for the effects of puberty and sex. Three midline regions (medial prefrontal, pregenual anterior cingulate, and posterior cingulate), within the DMN and consistently implicated in mood disorders, were selected as seeds. Within- and between-network clusters of the DMN iFC changed with pubertal maturation differently in boys and girls (puberty-X-sex). Specifically, pubertal maturation predicted weaker iFC in girls and stronger iFC in boys. Finally, iFC was stronger in boys than girls independently of puberty. Brain-behavior associations indicated that lower connectivity of the anterior cingulate seed predicted higher internalizing symptoms at 2-year follow-up. In conclusion, weaker iFC of the anterior DMN may signal disconnections among circuits supporting mood regulation, conferring risk for internalizing disorders.

Reward-centricity and attenuated aversions: An adolescent phenotype emerging from studies in laboratory animals

Adolescence is an evolutionarily conserved developmental period, with neural circuits and behaviors contributing to the detection, procurement, and receipt of rewards bearing similarity across species. Studies with laboratory animals suggest that adolescence is typified by a "reward-centric" phenotype-an increased sensitivity to rewards relative to adults. In contrast, adolescent rodents are reportedly less sensitive to the aversive properties of many drugs and naturally aversive stimuli. Alterations within the mesocorticolimbic dopamine and endocannabinoid systems likely contribute to an adolescent reward-sensitive, yet aversion-resistant, phenotype. Although early hypotheses postulated that developmental changes in dopaminergic circuitry would result in a "reward deficiency" syndrome, evidence now suggests the opposite: that adolescents are uniquely poised to seek out hedonic stimuli, experience greater "pleasure" from rewards, and consume rewarding stimuli in excess. Future studies that more clearly define the role of specific brain regions and neurotransmitter systems in the expression of behaviors toward reward- and aversive-related cues and stimuli are necessary to more fully understand an adolescent-proclivity for and vulnerability to rewards and drugs of potential abuse.