People who work rotating shifts outside the typical 9 to 5 window are more likely to be depressed, researchers say.
A study that followed more than 175,000 British adults found that shift workers – such as nurses, security guards and police officers – were 22 percent more likely to be diagnosed with the condition than those on a standard daytime schedule.
They were also 16 percent more likely to have anxiety.
However, the scientists did not find that the self-employed were more likely to be depressed, as were those who routinely work night shifts – contrary to many previous studies.
Researchers suggested this was because night shift workers had adapted to the changed lifestyle, meaning they were no longer overtaken by the severe fatigue that caused others’ mental health problems.
A study that followed more than 175,000 British adults found that shift workers – such as nurses, security guards, police officers and journalists – were 22 per cent more likely to be diagnosed with the condition than their day-working counterparts (stock image)
More than 15 million Americans — or about one in five working adults — work shifts, according to the Bureau of Labor Statistics.
Researchers have known for years that this is linked to damage to physical health, including an increased risk of heart disease, diabetes and dementia.
For the study, researchers at Huazhong University in Wuhan, China, drew numbers from the UK Biobank – a database of in-depth genetic and health information on more than 500,000 Britons.
Data was used from 175,000 employees or self-employed, including nearly 28,000 shift workers – or 16 percent of the total.
These individuals averaged their late 40s to early 50s and were first recruited into the Biobank between 2006 and 2010.
They had been employed for an average of 12 years and worked 34 to 38 hours a week.
Each was followed for about nine years and asked to report whether they were diagnosed with depression or anxiety.
The study defined shift work as jobs that require people to work outside of the typical 9 a.m. to 5 p.m. time frame, such as jobs that start in the afternoon, evening or night or where shifts are rotated.
During the study period there were 3,956 new cases of depression – 2.3 percent of the total – and 2,838 new cases of anxiety – or 1.7 percent.
Dr. Minzhi Xu, a health expert at Huazhong University in Wuhan, China, and others wrote in the paper that poor mental health among shift workers was partly explained by fatigue and lifestyle factors.
They pointed to a higher likelihood of smoking and poor sleep and being overweight or obese among shift workers as causes of mental health problems.
Some research has linked smoking to depression, with theories suggesting it may be due to nicotine dependence. Psychological problems can arise during a low point, when someone has not had a cigarette for a long time, or during the struggle to quit smoking.
Poor sleep is also linked to a bad mood, as it disrupts emotional regulation and leads to higher stress levels in the body.
A higher BMI can also indicate psychological problems, because people are more sedentary or have an unhealthy diet, which can lead to problems. It can also indicate an emotional problem that causes overeating.
The researchers also noted that shift workers are more likely to have lower incomes and live in poverty-stricken environments, which also increases the risk of mental health problems.
However, the study also found that night shift work was not more significantly associated with depression than day shift work.
The scientists suggested that this was because a person had adapted to the anomalous schedule over time, leading to reductions in fatigue and recovery of mental health.
The results differed from other studies, but scientists said this may be because they defined night shifts as working between noon and 6 a.m. In comparison, newspapers from the Netherlands have defined a night shift as a shift that starts after 10 p.m.