Take notice of the woman's sleep and eating behaviors. Married women that are unhappy are also often depressed. Penn State University states, "Individuals may sleep more or sleep less; they may even change eating patterns when depressed."

Jot down a list of items that are different in your wife's life from six months ago. An unfavorable change in a job or pay cut may indicate that the woman is unhappy or feeling down.

Learn the signs of a cheating spouse. Often when a woman appears unhappy in a marriage, there is the possibility of an affair. Pay attention to her attitude. Women that are cheating act secretive and defensive about their actions and whereabouts and demand privacy. The Dating Advice Secrets website also says, "Women that are cheating improve their appearances through buying new clothing, exercising and improving their lifestyles."

Search the house for alcohol or drugs. Look in closets, drawers and cupboards. Keep track of bottles in liquor cabinets weekly for changes. Some women may drink or use drugs to cope with being unhappy.

Talk with close friends and family members about your concerns. Ask them if they have noticed any behaviors that would indicate that your wife is unhappy. Pay attention to how they react to questions. Close friends of your wife may know things that you do not. Watch and make mental notes if your wife's friends avoid making direct eye contact with you or fidget while speaking.

Sit down with your wife and have a heart-to-heart talk. Voice your concerns that you feel that she may be unhappy. Listen with sympathy and without judgement if she describes what is making her despondent. The University of Michigan says, "In a healthy relationship, both partners are able to express their thoughts, feelings and needs without fear of being judged. Communication is one of the essential building blocks to having a successful marriage."