Sample Characteristics and Attrition in the Wisconsin Longitudinal Study.

Note: p-value is from t- or chi-squared test for the difference between the study and attrition samples, and s.d. denotes standard deviation. Attrition sample consists of participants who lacked information either regarding depression or regarding sleep. Some had one but not other, allowing comparison against those with both. For such cases, n denotes sample size for this sub-sample.