3. Sleep disorders

Sleep disorders are conditions that interfere with your normal capacity to sleep. They negatively impact the way you are sleeping. And they are more common than you might think: more than 100 million Americans are not getting enough sleep!

From basic insomnia to narcolepsy and sleep apnea, these conditions affect the REM cycles and, thus, your dreaming capacity.

4. Certain medications 

The way medications affect us differs from individual to individual. The side effects can range from mild, like a dry mouth or sleepiness, to more severe ones, like seizures or coma.

One unusual side effect is that some types of medications can induce nightmares and vivid, disturbing dreams. These dreams are usually very distressing and affect our ability to rest. Also, when we wake up from such dreams, we can feel all sweaty and terrified, maybe even shaken, but we don’t usually remember those bad dreams.