I’d heard this factoid before, and was naturally skeptical. Still, Steven Stack, Occupation and Suicide, 82 Social Science Quarterly 384, 392 (2001) so reports. Controlling for various demographic factors, and using 1990 data from 21 states (covering 6198 suicides and 137,687 natural deaths) dentists had an odds ratio of 5.43 (compared to all the people in the sample), much higher than the nearest runner-up, doctors (2.31). Both the dentists’ and the doctors’ odds ratios were statistically significant.
The lowest statistically significant odds ratios were among farm workers (0.69) and clerks (0.85). Professors and lawyers both were not statistically different from the average person in the sample.