Figure 1.

Percentage of Stage 3 sleep across age strata for the controls (a), and alcohol‐ (b) and cocaine‐dependent (c) groups. A significant group × age interaction for percentage of Stage 3 sleep was found (F = 2.28, P < 0.05). Data are presented as means ± standard error (SE). Adjusting for multiple comparisons, Sidak corrected between‐group differences were identified: +P < 0.10, *P < 0.05, **P < 0.001. Effect sizes (d) a,b, a–c, b,c: age group, 25–32 years: 1.52, 2.37, 0.89; age group, 33–40 years: 0.20, 0.86, 1.06; age group, 41–48 years: 1.12, 1.60, 0.48; age group, 49–60 years: 0.42, 1.19, 0.77