NEW YORK - Manual laborers in the U.S. who tend to work in isolation and who face unsteady employment have the highest rate of suicide, according to a broad federal study.

The Centers for Disease Control and Prevention found that farmers, lumberjacks and fishermen kill themselves most often. High rates were also seen in carpenters, miners, electricians and people who work in construction. Mechanics were close behind, according to the study, which showed enormous differences of suicide rates across jobs.

Dentists, doctors and other health care professionals had an 80 percent lower suicide rate than the farmers, fishermen and lumberjacks. The lowest rate was in teachers, educators and librarians.

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Suicide rates have risen in recent years, increasing 21 percent from 2000 to 2012 for Americans at least 16 years of age.

The CDC report is perhaps the largest U.S. study to compare suicide rates among occupations. But it is not comprehensive. It only covers 17 states, looking at about 12,300 of the more than 40,000 suicide deaths reported in the entire nation in 2012.

Wendy McIntosh, one of the authors of the report and a health scientist in the CDC's division of violence prevention, pointed to a main takeaway of the study: "Knowing suicide rates by occupation provides employers and other prevention professionals with an opportunity to focus on suicide prevention programs and messages."

The research can help guide employers or industries develop their strategies for reducing the incidence of suicide, McIntosh added. Those plans can include ensuring that employee assistance and workplace programs are in place to help managers and other staff recognize warning signs, as well providing technology-based mental health tools. Companies should also make sure workers know how to reach the National Suicide Prevention Hotline, at (800) 273-TALK (8255).

Because of the limited data, they could calculate suicide rates only for broad occupation categories, but not for specific jobs. The categories, which sometimes seem to group professions that have little to do with each other, like athletes and artists, are based on federal classifications used for collecting jobs-related data.

So it's not clear what the suicide rate is just for farmers. Or for mathematicians. Or journalists.

"Occupational groups with higher suicide rates might be at risk for a number of reasons, including job-related isolation and demands, stressful work environments, and work-home imbalance, as well as socioeconomic inequities, including lower income, lower education level, and lack of access to health services," the CDC said in the report. "Previous research suggests that farmers' chronic exposure to pesticides might affect the neurologic system and contribute to depressive symptoms."

Suicide is the nation's 10th-leading cause of death. Public attention often focuses on teens and college students, but the highest numbers and rates are in middle-aged adults. Suicide is far more common in males, and the rankings largely reflect the male suicide rates for each group.

The highest female suicide rate was seen in the category that includes police, firefighters and corrections officers. The second-highest rate for women was in the legal profession.

It's not the first time a suicide problem has been noted for some of the jobs. In the 1980s, media reports detailed high suicide rates in Midwestern farmers. That was attributed to a tough economy and farmers use of pesticides that scientists have theorized may cause symptoms of depression.

The CDC's occupational suicide list:

1. Farmworkers, fishermen, lumberjacks, others in forestry or agriculture (85 suicides per 100,000)

2. Carpenters, miners, electricians, construction trades (53)

3. Mechanics and those who do installation, maintenance, repair (48)

4. Factory and production workers (35)

5. Architects, engineers (32)

6. Police, firefighters, corrections workers, others in protective services (31)

7. Artists, designers, entertainers, athletes, media (24)

8. Computer programmers, mathematicians, statisticians (23)

9. Transportation workers (22)

10. Corporate executives and managers, advertising and public relations (20)

11. Lawyers and workers in legal system (19)

12. Doctors, dentists and other health care professionals (19)

13. Scientists and lab technicians (17)

14. Accountants, others in business, financial operations (16)

15. Nursing, medical assistants, health care support (15)

16. Clergy, social workers, other social service workers (14)

17. Real estate agents, telemarketers, sales (13)

18. Building and ground, cleaning, maintenance (13)

19. Cooks, food service workers (13)

20. Child care workers, barbers, animal trainers, personal care and service (8)