Objective: To evaluate the impact of psoriasis (PsO) on the presence of co-morbidities in the first year after the diagnosis. Methods: A retrospective study of the PharMetrics database, compiled from managed care plans throughout the United States, from January 1, 2000 through December 31, 2006 was conducted. Patients between the ages of 18 to 80 years, who had a minimum of 12 months of continuous enrollment before and after their index diagnosis with PsO, were included. The index diagnosis date was derived from the first claim for PsO during the study period. The presence of co-morbidities was determined by frequency counts and as a percentage of total claims generated during the study period. Results: The study cohort included 48,068 patients; 52.3% were females, and the mean age was 46.3 years. Multiple co-morbidities were identified in the years prior to and subsequent to the diagnosis of PsO. The five most frequently observed co-morbidities were: hypertensive disease (increased from 24.45% to 26.65%), hyperlipidemia (from 15.72% to 18.06%), pure hypercholesterolemia, pure hyperglyceridemia, and mixed hyperlipidemia (from 14.65% to 16.18%), diabetes mellitus (from 8.36% to 9.57%), depressive disorder, episodic mood disorder, and dysthemic disorder (from 6.88% to 7.12%). Additionally, the five highest percentage increases in co-morbidities in the years prior to and subsequent to the diagnosis of PsO were: 1) Malignant neoplasm of uterus and cervix uteri (60%, pre-n=26, post-n=38); 2) Malignant neoplasm of trachea, bronchus and lung (57.1%, pre-n=33, post-n=54); 3) Malignant neoplasm of ovary and other uterine adnexa (44.4%, pre-n=42, post-n=63); 4) Psoriatic Arthropathy (44.0%, pre-n=1357, post-n=1950); and 5) Atherosclerosis (33.3%, pre-n=142, post-n=193). Conclusion: This study indicates that co-morbidities increase significantly in the year subsequent to a diagnosis of PsO. The large increases noted in malignancies may be due to the small numbers of cases observed.