We dream every night, although we do not necessarily register the dreams within long-term memory, so many people forget all or most of their dreams upon waking. To be more specific, we go through certain “waves” of sleep traceable by rapid eye movements (REM).
The most active cycle of REM tends to happen around every 90 minutes for most people, and those are when we experience the most narrative-driven dreams as opposed to the mere images and thoughts that are flashed in the unconscious mind during sleep.
These are usually what we are talking about when we talk about “dreaming” and the ones most likely to stick to memory upon waking, if at all. Assuming a period of 8 hours of sleep, this means we have about 5-6 narrative dreams per night.
Consuming media, or being under certain influences of drugs, or experiencing states of emotion like anxiety and stress can alter these patterns of REM, however, and therefore affect not only how often we produce narrative dreams but also how well we recall them.
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