Flashbacks can be caused by hallucinogenic drugs, and it’s quite common for many who’ve used drugs to experience; for some the flashbacks may be bothering, while others may not find them troublesome. There are times when these flashbacks can be intense, frequent, and quite unpleasant, even for those who are currently abstaining from drug use. The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) has documented that recurring flashbacks after drug effects have worn off are medical phenomena known as hallucinogen persisting perception disorder (flashbacks).
Symptoms of Hallucinogen Persisting Perception Disorder include:
- An image of an object despite it not being there anymore (palinopsia)
- False perceptions of movement out of the corner of the eye (peripheral vision)
- Flashes of color
- Hallucinations (especially of geometric forms)
- Halos or trailing after-effects of images
- Inanimate objects appearing alive (for example, walls that appear to be “breathing” or growing)
- Intensified color
- Objects appearing larger than they are (macropsia)
- Objects appearing smaller than they are (micropsia)
- Trails of images of moving objects
- Visual snow or air that looks grainy or textured
This disorder is often diagnosed in people who have history of substance use, and can occur even after using the triggering drug just once. These triggering drugs include marijuana, phencyclidine (PCP), and methylenedioxymethamphetamine (MDMA). Co-occuring mental illnesses such as anxiety, Bipolar disorder, Major depressive disorder, and Schizophrenia are also common in people diagnosed with HPPD. If you or someone you know is experiencing symptoms of HPPD do not hesitate to talk with your health provider to find best treatment options.
Reference: https://www.verywellmind.com/what-are-flashbacks-and-what-causes-them-22087
