Mushroom Spine Densities. Mushroom spines were counted in 40 μm segments midway down the basal dendrites and at the distal termination, and in 50 μm segments midway and at the distal termination for apical dendrites and averaged to create a final spines/μm density for adolescent and adult males and females. (* = p < 0.05, post-hoc 3-way interaction; ‡ = p < 0.05, age effect; # = p < 0.05, sex effect; † = p < 0.05, stress effect). A. Layer II/III.1. Basal Dendrites. Age decreased spine density. There was an interaction of Age*Sex*Stress such that stressed female adolescents had greater spine density than stressed male adolescents, stressed female adults, female adult controls, adult male controls and stressed adolescent males. Stress reduced spine density in male adolescents. Group sizes were: n = 9 cells/4 rats for male adult controls, 10 cells/4 rats for stressed male adults, 9 cells/4 rats for male adolescent controls, 10 cells/4 rats for stressed male adolescents, 7 cells/4 rats for female adult controls, 14 cells/4 rats for stressed female adults, 11 cells/4 rats for female adolescent controls, 10 cells/4 rats for stressed female adolescents]. 2. Apical Dendrites. There was no effect on mushroom spine density. Group sizes were: n = 9 cells/4 rats for male adult controls, 10 cells/4 rats for stressed male adults, 9 cells/4 rats for male adolescent controls, 10 cells/4 rats for stressed male adolescents, 7 cells/4 rats for female adult controls, 14 cells/4 rats for stressed female adults, 11 cells/4 rats for female adolescent controls, 10 cells/4 rats for stressed female adolescents. B. Layer V.1. Basal Dendrites. Spine density increased with age overall regardless of sex or stress. Stress decreased spine density. Group sizes were: n = 10 cells/4 rats for male adult controls, 9 cells/4 rats for stressed male adults, 11 cells/4 rats for male adolescent controls, 10 cells/4 rats for stressed male adolescents, 9 cells/4 rats for female adult controls, 10 cells/4 rats for stressed female adults, 10 cells/4 rats for female adolescent controls, 11 cells/4 rats for stressed female adolescents. 2. Apical Dendrites. Females had greater spine density than males regardless of stress or age. Stress also decreased spine density regardless of age or sex. This was driven by stress decreasing spine density in male adolescents and female adults. Adult female controls had greater spine density than adult male controls or adolescent female controls. Group sizes were: n = 10 cells/4 rats for male adult controls, 9 cells/4 rats for stressed male adults, 11 cells/4 rats for male adolescent controls, 10 cells/4 rats for stressed male adolescents, 9 cells/4 rats for female adult controls, 10 cells/4 rats for stressed female adults, 10 cells/4 rats for female adolescent controls, 11 cells/4 rats for stressed female adolescents.