I've wondered that exact same thing... Since we can pull up "repressed" or buried memories, I'm assuming the opposite (burying them deeper than they were before) can also be done... That's a good question though. I've had some lucid dreams where I become so intensely involved that I've woken up with headaches -usually due to extreme concentration or "battles" where I can feel the fluid in my brain and in my spinal cord moving or circulating... kinda freaky. I don't know about causing brain damage, but I would suppose it's possible. Ithink it's been asked before on the forum somewhere, but does anyone know of any good studies done or being done on the physical effects or side effects of LDing?