Heritability of plasma neopterin levels in the Old Order Amish.

BACKGROUND: We examined the heritability of neopterin, a biomarker for cell-mediated immunity and oxidative stress, and potentially for psychiatric disorders, in the Old Order Amish. METHODS: Plasma neopterin levels were determined in 2015 Old Order Amish adults. Quantitative genetic procedures were used to estimate heritability of neopterin. RESULTS: Heritability of log-neopterin was estimated at 0.07 after adjusting for age, gender, and household (p=0.03). The shared household effect was 0.06 (p<0.02). CONCLUSIONS: We found a low heritability of neopterin and small household effect, suggesting that non-household environmental factors are more important determinants of variance of neopterin levels in the Amish.

Test-retest reliability of the Seasonal Pattern Assessment Questionnaire in Old Order Amish.

BACKGROUND: Research on test-retest reliability of the Season Pattern Assessment Questionnaire (SPAQ) is sparse, and to date, has not been done with subgroups such as the Old Order Amish. METHODS: We examined the test-retest reliability of the SPAQ in a sample of Old Order Amish. A total of 68 Old Order Amish participants completed the SPAQ twice, with 4 months between administrations. Quantitative data analyses were carried out to determine respective strengths of test-restest reliability for two variables [i.e., Global Seasonality Score (GSS), and Problem Rating Score (PRS)]. RESULTS AND CONCLUSIONS: Results revealed the test-retest reliability of the SPAQ in this population to be strong within the respective variables (GSS, α= 0.87; and PRS, α= 0.79) using Cronbach's alpha.

Seasonality of mood and behavior in the Old Order Amish.

BACKGROUND/OBJECTIVE: We examined seasonality and winter seasonal affective disorder (SAD) in the Old Order Amish of Lancaster County, Pennsylvania, a unique population that prohibits use of network electric light in their homes. METHODS: We estimated SAD using the seasonal pattern assessment questionnaire (SPAQ) in 1306 Amish adults and compared the frequencies of SAD and total SAD (i.e., presence of either SAD or subsyndromal-SAD) between men and women, young and old, and awareness of (ever vs. never heard about) SAD. Heritability of global seasonality score (GSS) was estimated using the maximum likelihood method, including a household effect to capture shared environmental effects. RESULTS: The mean (±SD) GSS was 4.36 (±3.38). Prevalence was 0.84% (95% CI: 0.36-1.58) for SAD and 2.59% (95% CI: 1.69-3.73) for total SAD. Heritability of GSS was 0.14±0.06 (SE) (p=0.002) after adjusting for age, gender, and household effects. LIMITATIONS: Limitations include likely overestimation of the rates of SAD by SPAQ, possible selection bias and recall bias, and limited generalizability of the study. CONCLUSIONS: In the Amish, GSS and SAD prevalence were lower than observed in earlier SPAQ-based studies in other predominantly Caucasian populations. Low heritability of SAD suggests dominant environmental effects. The effects of awareness, age and gender on SAD risk were similar as in previous studies. Identifying factors of resilience to SAD in the face of seasonal changes in the Amish could suggest novel preventative and therapeutic approaches to reduce the impact of SAD in the general population.