Sleep and depression have a complex relationship. In some cases depression can cause sleep problems, such as insomnia, and in other cases sleep problems contribute to depression. Sleep issues and depression share common risk factors, and certain treatments can relieve symptoms of both. As researchers delve more into this relationship, new understanding of the conditions could lead to new treatments.

Who is at risk?

Though depression – and sleep problems for that matter – can affect anyone, certain people are more susceptible, including women and older adults. Higher rates of depression and sleep problems are reported in older adults likely due to illness. For women, hormonal changes due to menopause, pregnancy and menstruation can contribute to depression. It’s also possible that within these two groups, higher rates of insomnia actually cause higher rates of depression.

            [SLIDESHOW: 8 Health Issues that Cause Sleep Problems]

How are insomnia and depression linked?

According to the National Sleep Foundation, studies have shown that people who experience insomnia are 10 times more likely to become depressed compared with those who consistently get good sleep. In addition, people who are depressed have a higher frequency of experiencing insomnia. The symptoms can include difficulty falling asleep, difficulty staying asleep, not getting deep sleep and daytime sleepiness. Research suggests that people who have problems both falling asleep and staying asleep are at greater risk for depression. In addition, some medications used to treat depression can cause sleep disturbances.

What about sleep apnea?

According to a study from the Centers for Disease Control and Prevention (CDC), Obstructive sleep apnea (OSA) is associated with depression, regardless of weight, age, sex or race. The study analyzed survey data from 9,714 adults in the United States and found that the likelihood of depression increased with the reported frequency of snorting and paused breathing during the night.

Researchers suggest that better screening for OSA and depression could help address these frequently underdiagnosed conditions, especially if sleepiness is a problem.

            [SLIDESHOW: 7 Things that Worsen Sleep Apnea]

Does depression cause fatigue?

A May 2012 study looked at 508 children with ADHD who were also suffering from daytime fatigue. Researchers found that although these kids were getting enough sleep at night, they were still experiencing excessive daytime sleepiness, attention and hyperactivity problems and learning difficulties. Kids without excessive daytime sleepiness did not have attention or learning problems. Researchers then found that obesity, inattention, depression, anxiety, asthma, and parental insomnia all contributed to the children’s daytime fatigue.