Depression and other changes in behavior may come before memory loss in seniors who eventually develop Alzheimer’s disease.

A new study raises as many questions as it answers about the early, non-cognitive symptoms of dementia. Non-cognitive symptoms involve emotions and self-control. Cognitive symptoms involve thinking and memory.

Researchers from the Washington University School of Medicine analyzed seven years of data on people older than 50. Of the 2,416 people in the study, slightly more than half developed dementia during the study period.

These patients also developed behavioral changes, including apathy, irritability, and depression sooner than those who didn’t go on to get dementia. The remaining volunteers stayed cognitively normal, with no reported memory problems.

“We are trying to get a picture of some of the symptoms that occur along with memory and thinking problems when people get early dementia,” said study author Catherine Roe, Ph.D., an assistant professor of neurology at the Washington University School of Medicine.

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After four years of study, 30 percent of the people who would later develop dementia had symptoms of depression. Just 15 percent of those who did not go on to develop dementia had depression. Those who developed dementia also had more problems with the activities of daily living, such as paying bills, shopping, and preparing meals. There was no major difference in the results based on gender.

Previous research shows that non-cognitive symptoms affect about 90 percent of patients with Alzheimer’s disease. But if you’re feeling down, or notice that your spouse has become more irritable lately, don’t jump to worst-case conclusions just yet.

“Don’t look at any of these as pointing to higher risk of dementia,” Roe said. “People can be depressed or have lack of energy for many reasons. But this helps give us a clearer picture of what early Alzheimer’s disease looks like.”

According to the Alzheimer’s Foundation of America, while depression may cause or worsen memory loss in those who already have cognitive impairment, doctors still don’t know whether depression without cognitive impairment increases the risk of developing Alzheimer’s.

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Study volunteers took a series of standardized tests that measured any decline in thinking, memory, behavior, and functional skills. Researcher noticed changes in both groups — those who did and did not end up with dementia.

“We were somewhat surprised that the order of symptom occurrence was the same for people who did and did not develop Alzheimer’s disease,” Roe said.

Symptoms occurred in three phases. Irritability, depression, and nighttime behavior changes developed first. This was followed by anxiety, appetite changes, agitation, and apathy. Finally, elation, mobility disorders, hallucinations , delusions, and impulsive, inappropriate behavior were reported.

People who were diagnosed with dementia developed these symptoms sooner. The results suggest that a series of non-cognitive changes begins before memory symptoms appear in Alzheimer’s disease.

While Roe is encouraged by the study results, she said it’s still unclear whether depression and other non-cognitive symptoms are a response to what’s going on in the brain as Alzheimer’s develops, or if they’re caused by the same underlying changes.

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Behavioral and psychological changes could also be a sign of other underlying conditions, so be sure to speak with your doctor, Roe said.

It’s also important for doctors to look beyond the usual suspects, such as anemia in someone complaining of low energy. “Maybe they should also consider giving the person some sort of memory or cognitive screening. This could help pinpoint some other areas that might need to be explored,” said Roe.

This study only included people who had no symptoms of depression or memory loss at the beginning of the analysis. Since depression is relatively common in seniors, Roe said a more realistic sample would have included volunteers with some depression symptoms.

“We were just really interested in learning when these symptoms occurred relative to each other,” Roe said.

She stressed that some of the people who didn’t develop dementia during the study might still have gone on to develop it later.