Hesitation to take antidepressant drugs is keeping patients from telling doctors about depression symptoms, a new study says.

The paper, released Monday in the journal Annals of Family Medicine, was researched by a team led by Robert A. Bell of the University of California, Davis.

Researchers surveyed 1,054 adults about why they wouldn't tell their primary care physician about depression symptoms, as well as their beliefs about the mental disorder.

The study found that 43 percent of the participants said they had at least one reason not to tell their doctors about their depression. And 22.9 percent did not tell their family doctor because they thought he or she would recommend antidepressants.

Concerns about side effects may be a major reason for the reluctance. The most common include constipation, headaches, dizziness, sleep problems and weight gain.

Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behavior, feelings and physical well-being.

A number of psychiatric syndromes feature depressed mood as a main symptom.

Depression is associated with changes in substances in the brain that help nerve cells communicate (neurotransmitters) such as serotonin, dopamine and norepinephrine. The levels of these neurotransmitters can be influenced by, among other things, physical illnesses, genetics, hormonal changes, medications, aging, brain injuries, seasonal light cycle changes and social circumstances.

When a person has depression, it goes beyond feeling sad. Intense feelings of sadness and other symptoms, like losing interest in things you enjoy, may last for a while. Depression is a medical illness, not a sign of weakness.

Within depression, major depressive disorder, commonly called major depression, or clinical depression, is a condition where a person has at least two weeks of depressed mood or a loss of interest or pleasure in nearly all activities. Dysthymia is a state of chronic depressed mood, the symptoms of which do not meet the severity of a major depressive episode. People suffering bipolar disorder may also experience major depressive episodes.