Thousands of Utahns share a common nightmare.

Psychiatrists formally call it affective disorder; most people know it as depression.And the nightmare is growing. Local psychiatrists speculate that at least one of every 25 people is afflicted by the condition.

Coping with it is especially common at Christmas when people's expectations are highest.

"It's supposed to be the happiest time of the year because it gives adults the permission to be children again - to relive a time when everything was fanciful and fantasy, and all our dreams came true," said Dr. Daniel D. Christensen, clinical professor of psychiatry at the University of Utah Medical Center.

The unfortunate reality, he said, is that holiday joy is often dampened by stress, drudgery and unfulfilled expectations.

The result is depression.

Christensen, medical director of the Western Institute of Neuropsychiatry, said it is sometimes a challenge for sufferers to distinguish between psychological or biological depression. Their symptoms are similar.

Biological depression, or seasonal affective disorder, is thought to be related to the amount of sunlight a person receives. As many as 10 percent of Utahns suffer from it regularly during the dark winter months.

Those afflicted generally feel fatigued, sleep and eat more. In severe cases they feel despair and hopelessness, and may even entertain thoughts of suicide.

Medications, or going South for the winter, are helpful treatments for biological depression. Suffererscan use full-spectrum light sources to artificially lengthen their eight-hour winter days. By reading or relaxing next to the lights, they can actually fool the body into thinking it's light outside.

Psychological depression, Christensen said, is much more difficult to treat. It's also more common - especially during the holidays.

"Holidays portray the ideal - love, brotherhood, prosperity, family unity," Christensen said. "It holds the hope, if not the expectation of joy, resolution of discord."

Yet annually people's hopes are dashed. People who don't have a family or whose family is not a happy one are especially bothered by holiday blues.

"Some have an increased sense of isolation and worthlessness. The emphasis on brotherhood and family togetherness points out their deprivation. The season is a yearly reminder of their loneliness."

Christmas, Christensen said, also carries with it stresses - generally associated with financial strains.

"The holidays are sort of a permission for excesses - excesses of spending, eating, partying, revelry and drinking," he said. "Some people cope by the use of drugs and alcohol."

He said holiday problems are best dealt with by anticipating and planning for them. Here are some of his recommendations for coping:

-Families that have a history of holiday turmoil should work on strategies to make things go differently. They may have to change family traditions, alter plans, lower expectations.

"The perfect rarely happens anyway," he said. "The best present for some families might be family peace."

-Be content with yourself, your family and what you have, rather than being whipped about by commercials and worldly competition.

-Give everyone a role. "Kids need to be part of the holiday preparations and setting of family traditions."

-Set realistic expectations. "The holidays often don't fulfill a person's fantasies. If family conflicts and world turmoil aren't resolved in the other 364 days, it's unlikely to happen on Christmas Day."

-Set realistic budgets.

-Don't seek the perfect gift. "Excessive gift giving is sometimes driven by guilt - to make up for what's missing the rest of the year," Christensen said. "It's often an overcompensation to win affection and acceptance.

"What children need at Christmas is having that special assurance that they are loved and are very special."

-People suffering depressions that are not manageable should seek professional help.