Heard this one before. The problem with this is that there are many people who are always lucid when they dream, every single night, and have been this way for probably their whole lives. We call them "naturals." These naturals don't seem to be any different from us non-lucid dreamers in terms of memory or any other measure. Fact is, there is no evidence
whatsoever which suggests that lucid dreaming has
any detrimental side effects, physical or mental.
By the way, that sounds like a pretty interesting documentary

. Do you happen to remember the name?
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