Immediate effects Small quantities of cannabis can have effects that last 2 to 3 hours after smoking. They may feel less inhibited, friendlier and laugh spontaneously. Sometimes people become quiet and reflective. They may also become sleepy. It can affect vision and perception of time and space.
People can lose track of what they are saying or thinking.
When affected by cannabis, some people may think as though they've had profound ideas or insights. Other common immediate effects include increased heart rate, low blood pressure, faintness and reddened eyes. There also can be a 'hangover' effect, like drowsiness and poor co-ordination that lasts for several hours after the initial effects. In greater quantities Larger quantities of marijuana make the above effects stronger, and also tend to distort a person's perceptions. Currently, there is no evidence that occasional use of small quantities of cannabis causes any permanent health damage.