New research has associated depressive symptoms in midlife, or late in life, with an increased risk of developing dementia.

According to research, appearing in the current issue of the Archives of General Psychiatry, depressive symptoms that occur from midlife are associated with an increased risk of developing vascular dementia, while symptoms that occur in late life only are more likely to be early signs of Alzheimer's disease.

Researchers at the University of California at San Francisco and healthcare provider Kaiser Permanente, explained that vascular dementia, the second most common type of dementia, develops when impaired blood flow to parts of the brain deprives cells of nutrients and oxygen.

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"The findings have important public health implications because they raise hope that adequate treatment of depression in midlife may reduce dementia risk, particularly vascular dementia, later in life," said Rachel Whitmer, PhD, a research scientist at the Kaiser Permanente Northern California Division of Research and the principal investigator of the study, in a statement.

The results comes from a study of more than 13,000 long-term members of the Kaiser Permanente Northern California integrated care delivery system, examining the association between depressive symptoms and dementia over the course of 45 years.

Participants were evaluated for depressive symptoms in midlife and again in late life between 1994-2000.

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• A Change In Mood

  Is your partner unusually gloomy or sad? Do they put a negative spin on everything? Perhaps they have frequent angry outbursts - and these are aimed at you?

• Energy Levels

  For some, depression manifests as a massive loss of energy. If your partner is too tired and lethargic to do anything for a long period of time, consider whether something more serious is going on.

• Loss Of interest

  You might notice your partner cuts down on their activities, and loses interest in things they used to enjoy. In general, there's a sense of withdrawal.

• Getting Things Done

  You could find that your partner becomes overwhelmed by tasks and so avoids doing them. Even simple things such as putting the dirty dishes in the sink, can seem like a vast, vague 'problem'.

• Overdoing Things

  Sometimes as a person becomes depressed, they develop 'coping mechanisms', such as drinking more alcohol, using drugs, excess shopping, gambling, eating to excess, using pornography, or working extremely long hours - all ways to avoid dealing with negative feelings.

• Sex

  Your partner's sex drive may well be affected by depression, either by removing it or increasing their desire

• Anxiety

  It's likely that your partner may also develop stronger feelings of anxiety. For example, he or she may get really agitated about where the neighbours park their car. Or begin to dread doing something wrong, or doing work that's not good enough.

• Mornings

  First thing in the morning can be a really tough time for someone who's depressed, and it can take ages to get going. Many people say that as the day wears on they feel better.

• Communication

  You may start to feel you're treading on eggshells, as it becomes more easy to trigger a negative reaction. And if they are angry, they may hurl unfair accusations at you.

• Your Own Feelings

  You may begin to feel, hurt, rejected, isolated and guilty within your relationship - and perhaps embarrassed by their behaviour when in public. Take these feelings seriously, as they are an indicator something is wrong.