Beck et al. interviewed 50 patients diagnosed with depression aged 18 to 48 who were undergoing therapy, as well as a control group of 31 non-depressed patients, to understand cognitive distortions. Patients reported thoughts before and during therapy sessions and some kept thought diaries. Certain themes of low self-esteem, self-blame, feelings of being overwhelmed, anxiety, and paranoia appeared in depressed patients that were not present in the non-depressed group.