People with Parkinson's disease who show signs of depression may actually have a condition called demoralisation, according to a study published in Neurology, the medical journal of the American Academy of Neurology. 

Demoralisation is a state of feeling helpless and hopeless, with a self-perceived inability to perform tasks in stressful situations. With depression, a person usually knows the appropriate course of action and lacks the motivation to act. With demoralisation, a person may feel incompetent and therefore uncertain about the appropriate course of action. The two can occur together.

"The distinction between depression and demoralisation is important because the treatments approaches are different," said study author Brian Koo, MD, of Yale University in New Haven, Conn., and a member of the American Academy of Neurology. "Demoralisation may be better treated with cognitive behavioural therapy rather than antidepressant medication, which is often prescribed for depression."

For the study, researchers enrolled a total of 180 people with an average age of 68. Of the group, 94 people had Parkinson's disease and 86 people did not. Those in the control group were matched for sex, race, education and age.

Participants were evaluated for demoralisation with questionnaires asking questions such as "Do you experience feelings of helplessness, hopelessness or giving up?" and "Do you feel that you have failed to meet your expectations or those of other people?". They were also assessed for depression.

Researchers found that people with Parkinson's disease were 2.6 times more likely to be demoralized than people without the disease. In people with Parkinson's disease, 18%, or 17 of 94 people, were demoralised compared to 8%, or seven of 86 people in the control group.

Additionally, in the people with Parkinson's disease, 20%, or 19 of 94 people, were depressed compared to 4%, or three of 86 people in the control group.

While demoralisation and depression can occur at the same time, researchers found there were individuals with just one of the conditions. Among those with Parkinson's disease, 37%, or seven out of 19 people with depression were not demoralized. Also, 29% or five out of 17 people who were demoralized were not depressed.

"This suggests that demoralisation is not simply a marker of depression," Koo said.

Researchers also found that demoralisation, but not depression, was tied to the inability to control movement.

Koo said, "Since our research shows a link between demoralisation and a person's ability to function, more research may help further define how to best treat demoralisation in Parkinson's disease."

One limitation of the study was a lack of information on details of employment. Another was that Parkinson's patients with severe disease were more likely to not participate, so the prevalence of demoralisation may be underestimated.