Stress doesn’t need an introduction. We all experience it and will continue to experience it in the coming weeks.

Stress is basically our body’s innate reaction to the “threats” we sense in our daily life. That can come in the form of a C on an essay or a change in our relationships. When we encounter a potential threat, a small region in our brains—the hypothalamus—sets off an alarm. The alarm sparks our adrenal glands, which are located above the kidneys, and they discharge a rush of hormones. Those hormones include adrenaline and the primary stress hormone, cortisol.

The adrenaline and cortisol produce changes in the body: They increase our heart rate. They elevate blood pressure and encourage high levels of sugar in the blood stream. The body’s stress response is self-regulating—all these changes return to normal once the detected threat has passed. But if there’s a constant detected threat or stress, the high cortisol levels can cause heart disease, depression, digestion problems, and sleep problems.

Now, dreams, like stress, are a substantial part of the lives of all animals. Neuroscientists now believe that sleep (and dreaming while sleeping) is crucial to brain development. Sigmund Freud, one of the first dream theorists, proposed that dreaming is a means of achieving desires—often the desires that are suppressed in conscious life. However, subsequent dream theorists and researchers have proposed instead that dreaming is an adaptation to anxiety.

In that line of thinking, researchers at Miami University studied the dreams of students on campus and discovered that people incorporate features of their stresses into their dreams. They also discovered that stress actually increases the emotionality experienced in dreams; the more stress you are under, the stronger your emotions during a dream.

To add to this relationship, Avi Sadeh of Tel Aviv University further investigated why some people sleep better when they’re stressed while others lose sleep. He found that those who tended to focus on their feelings during high stress phases were also more likely to sleep less. And, of course, less sleep meant even more stress.

In terms of dreaming, the lack of sleep was especially problematic, because dreams tend to aid us in coping with stress. Matthew Walker and his research team at the University of California found that dreams provide us with a form of “overnight therapy”. Most of our dreams occur in the REM stage of sleep, a crucial stage for our feeling mentally rested. During REM, stress chemicals are suppressed. In other words, our stress chemistry shuts down while the brain manages the emotional experiences in dreams.

But there are many other theories about how anxiety relates to dreams, particularly nightmares. Some theorists associate certain types of dreams with mood regulation, and others say that certain types of dreams play a role in committing certain events to memory. Another theory is that stress is the cause of recurring nightmares.