Hollie V. Thomas, DPhil, Director of the MSc Program in Psychiatry at Cardiff University, wrote in an article titled "Psychiatric Symptoms in Cannabis Users," published Aug. 1993 in the British Journal of Psychiatry:

“Cannabis use can lead to a range of short-lived symptoms such as de-personalisation, de-realisation, a feeling of loss of control, fear of dying, irrational panic and paranoid ideas…

The evidence that cannabis has a causative role in chronic psychotic or affective disorders is not convincing, although the drug may modify the course of an already established illness.”

Aug. 1993