Increased intrasubject variability in response time (ISVRT) is evident in healthy preschoolers at familial risk for bipolar disorder, suggesting it may be an endophenotype.

We wished to determine whether decreases in N-acetyl aspartate (NAA) and increases in myoinositol (mI) concentrations as a ratio of creatine (Cr) occurred in the dorsolateral prefrontal cortex (DLPFC) of pediatric offspring of parents with bipolar disorder (BD) and a healthy comparison group (HC) over a 5-year period using proton magnetic resonance spectroscopy ((1)H-MRS). Paticipants comprised 64 offspring (9-18 years old) of parents with BD (36 with established BD, and 28 offspring with symptoms subsyndromal to mania) and 28 HCs, who were examined for group differences in NAA/Cr and mI/Cr in the DLPFC at baseline and follow-up at either 8, 10, 12, 52, 104, 156, 208, or 260 weeks. No significant group differences were found in metabolite concentrations at baseline or over time. At baseline, BD offspring had trends for higher mI/Cr concentrations in the right DLPFC than the HC group. mI/Cr concentrations increased with age, but no statistically significant group differences were found between groups on follow-up. It may be the case that with intervention youth at risk for BD are normalizing otherwise potentially aberrant neurochemical trajectories in the DLPFC. A longer period of follow-up may be required before observing any group differences.