Mental illness was the biggest cause of claims under Friends Provident's income protection plan last year.
Twenty-four per cent of claims were due to mental disorders, including chronic fatigue syndrome and stress.
Musculoskeletal disorders accounted for 21 per cent of claims, followed by conditions such as bronchitis, asthma and glandular fever at 16 per cent, heart disease and strokes at 13 per cent, accidents at 11 per cent, cancers at 8 per cent and nervous system diseases at 7 per cent.
Total claims last year reached nearly £25m for both individual and group policies. Friends has 140,000 income protection policyholders.
It says the results show that an illness which may not be considered critical from a medical standpoint can still be disabling and have a severe impact on a customer's future earnings.
Head of protection marketing Peter Hamilton says: “In a perverse way, this does show how wise it is for people to consider the value of having income protection cover.
“Hopefully, these figures will serve to strengthen the importance of income protection in the financial planning process.”
PIFC Consulting head of technical services Mike Dowding says the results reinforce a trend that sees mental disorders topping the list of claims across the marketplace.
He says while employers place emphasis on looking after manual workers' backs to prevent musculoskeletal problems, they are not taking enough action in jobs where stress is a problem.
Dowding says: “Here is another piece of evidence that mental disorders are top of the list. Stress is one of the major things that employers have still to address properly.”