The relationship of age, anxiety, and serum immunoglobulins with crystallized and fluid intelligence.

Serum immunoglobulin concentrations (IgG, IgA, and IgM), cognitive performance (crystallized and fluid intelligence), and self-reports of anxiety were evaluated in 24 men and women 60-75 years, and 50 men and women, 30-45 years. Trait anxiety was an important factor relating to performance differences between the young and old on crystallized and fluid subtests. IgM was inversely related to performance in the older age groups. Anxiety was not related to serum immunoglobulin levels.