P4 suicidality screener: Literature synthesis and results from two randomized trials

To synthesize the literature on use of the P4 suicidality screener since its introduction in 2010 and to summarize results from 2 randomized clinical trials. A PubMed search was conducted from 2010 to 2023 to retrieve studies reporting on use of the P4. Also, data was extracted from the CAMMPS and SCOPE trials in which the P4 was periodically administered over 12 months when the 9th item of the PHQ-9 was endorsed. A total of 21 research studies using the P4 were found, of which 12 provided some data on P4 findings. Additionally, another 7 protocol papers reported intended use of the P4 as a study measure. In our 2 trials, the 9th item was endorsed 259 (12.5%) times in 2068 administrations of the PHQ-9. Higher risk suicidal ideation was identified in 4.1% (12/294) of CAMMPS participants and 2.8% (7/250) of SCOPE participants. No suicide attempts occurred over the 12 months in either trial. The P4 has had moderate use as a brief suicidality screener and is an efficient way to identify the small proportion of depressed patients with higher risk suicidality. Studies comparing the P4 with other common suicidality screeners would further inform use.