Depression has been proposed as both a risk factor and an early symptom of dementia. Studies have consistently shown that a history of depression is associated with an increased risk of developing Alzheimer’s later in life. 

But while the link is clear, there is still debate in the scientific community over which is actually the case – does depression make you more likely to develop Alzheimer’s or is it, in fact, one of the disease’s earliest symptoms? 

Evidence supports both interpretations

Studies suggest that if you were diagnosed with depression in your earlier years and then are diagnosed with Alzheimer’s in your later years, the two are more likely related than if the time between the two diagnoses was shorter. 

“This is consistent with the notion that depression is a risk factor for dementia,” says Sarah A. Chau, PhD, research associate, Neuropsychopharmacology Research Program, Sunnybrook Research Institute. “However, there also is evidence to the contrary since studies also have shown that being diagnosed with depression late in life may likely progress to dementia. That would suggest depression as an early sign of dementia.”

Additionally, scientists recently have coined a new term – mild behavioral impairment. This refers to characteristics such as feeling unmotivated, being impulsive and behaving inappropriately, but without memory loss or confusion. The theory is that mild behavioral impairment may signal the potential for dementia. 
Says Dr. Chau, “Clearly, more studies are needed to disentangle this complex interaction between depression and dementia.”

Watch for signs of depression

Symptoms of depression include:

• feelings of helplessness, hopelessness, or worthlessness
• lack of energy, fatigue
• irritability
• loss of interest in activities 
• difficulty concentrating or remembering
• confusion
• trouble sleeping

If these symptoms are present for weeks or if your loved one expresses thoughts of suicide, seek help.

Manage your risk

There are things you can do to keep your brain as healthy as possible:

• Heart disease may contribute to the link between depression and dementia, so follow a heart-healthy diet. 
• Smoking may increase the risk of both depression and cognitive decline – so kick the habit. 
• Get regular exercise, which may help with depression and protect against the progression to dementia.