of openness (assessed using the Revised NEO Personality Inventory), and this positive effect was apparent more than a year after the psilocybin session. According to the study authors, the finding is significant because "no study has prospectively demonstrated personality change in healthy adults after an experimentally manipulated discrete event". A further study by Griffiths in 2017 found that doses of 20 to 30 mg/70 kg psilocybin inducing mystical-type experiences brought more lasting changes to traits including altruism, gratitude, forgiveness and feeling close to others when they were combined with a regular meditation practice and an extensive spiritual practice support programme. Although other researchers have described instances of psychedelic drug usage leading to new psychological understandings and personal insights, it is not known whether these experimental results can be generalized to larger populations. Physical effects Common responses include pupil dilation (93%); changes in heart rate (100%), including increases (56%), decreases (13%), and variable responses (31%); changes in blood pressure (84%), including hypotension (34%), hypertension (28%), and general instability (22%); changes in stretch reflex (86%), including increases (80%) and decreases (6%); nausea (44%); tremor (25%); and dysmetria (16%) (inability to properly direct or limit motions). The temporary increases in blood pressure caused by the drug can be a risk factor for users with pre-existing hypertension. These qualitative somatic effects caused by psilocybin have been corroborated by several early clinical studies. A 2005 magazine survey of club goers in the UK found that nausea or vomiting was experienced by over a quarter of those who had used psilocybin mushrooms in the last year, although this effect is caused by the mushroom rather than psilocybin itself. In one study, administration of gradually increasing dosages of psilocybin daily for 21 days had no measurable effect on electrolyte levels, blood sugar levels, or liver toxicity tests. Perceptual distortions Psilocybin is known to strongly influence the subjective experience of the passage of time. Users often feel as if time is slowed down, resulting in the perception that "minutes appear to be hours" or "time is standing still". Studies have demonstrated that psilocybin significantly impairs subjects' ability to gauge time intervals longer than 2.5 seconds, impairs their ability to synchronize to inter-beat intervals longer than 2 seconds, and reduces their preferred tapping rate. These results are consistent with the drug's role in affecting prefrontal cortex activity, and the role that the prefrontal cortex is known to play in