Benign and time-limited visual disturbances (flashbacks) in recent abstinent high-potency heavy cannabis smokers: a case series study.

Eight high-potency heavy cannabis smokers who fulfilled DSM-IV-TR criteria for cannabis dependence sought treatment for outpatient detoxification. During routine psychiatric interview they reported the presence of visual disturbances when intoxicated and no prior history of LSD use. They all communicated the persistence of visual disturbances after ceasing cannabis use. Seven categories of visual disturbances were described when staring at stationary and moving objects: visual distortions, distorted perception of distance, illusions of movement of stationary and moving objects, color intensification of objects,dimmed color, dimensional distortion and blending of patterns and objects. Patients reported having 2-5 different categories of flashbacks up to 3-6 months after cessation of cannabis use. The described phenomena may be interpreted as a time-limited benign side effect of high-potency cannabis use in some individuals. A combination of vulnerability and use of large amounts of high potency cannabis seem to contribute to the appearance of this condition. Conclusions from uncontrolled case series should be taken with appropriate caution.