A new study suggests that depression, anxiety and other behavioral changes can be early warning signs that one is at risk of developing Alzheimer's disease.

We are already aware that people with Alzheimer's disease experience memory loss but we don't have a clear idea yet of what they experience before the diagnosis. Researchers at the Washington University School of Medicine in St. Louis began the study to answer this question.

The researchers followed 2,416 people, age 50 and above, who visited 34 Alzheimer's disease centers across the United States but were not diagnosed with the disease. During the seven-year follow-up period, more than half of them developed dementia.

Common changes observed among those who developed dementia include boredom, loss of appetite or excessive appetite, irritability and depression. These changes were seen earlier than those who did not develop dementia. For instance, 30 percent of those who developed dementia experienced depression after four years of the study compared to 15 percent who don't have dementia, according to the press release.

The researchers admitted that further study is needed to determine if it was depression that caused dementia or the reverse. They recommend those suffering from behavioral changes consult a physician to find out if those are symptoms of an underlying condition.

"I wouldn't worry at this point if you're feeling anxious, depressed or tired that you have underlying Alzheimer's, because in most cases it has nothing to do with an underlying Alzheimer's process," study author Catherine Roe, an assistant professor of neurology at Washington University School of Medicine, told HealthDay News.

"We're just trying to get a better idea of what Alzheimer's looks like before people are even diagnosed with dementia," Roe added. "We're becoming more interested in symptoms occurring with Alzheimer's, but not what people typically think of."

The study was published in the Jan. 14 issue of Neurology.