Even hardcore smokers can become anxious, panicky, suspicious or paranoid.
Cannabis affects your coordination, which is one of the reasons why drug driving is just as illegal as drink driving.
Some people think cannabis is harmless just because it’s a plant – but it isn’t harmless. Cannabis, like tobacco, has lots of chemical 'nasties', which can cause lung disease and possibly cancer with long-term or heavy use, especially as it is often mixed with tobacco and smoked without a filter. It can also make asthma worse, and cause wheezing in non-asthma sufferers.
Cannabis itself can affect many different systems in the body, including the heart: It increases the heart rate and can affect blood pressure.
If you’ve a history of mental health problems, then taking cannabis is not a good idea: It can cause paranoia in the short term, but in those with a pre-existing psychotic illness, such as schizophrenia, it can contribute to relapse.
If you use cannabis and have a family background of mental illness, such as schizophrenia, you may be at increased risk of developing a psychotic illness.
It is reported that frequent use of cannabis can cut a man's sperm count, reduce sperm motility, and can suppress ovulation in women and so may affect fertility.
If you’re pregnant, smoking cannabis frequently may have some association with the risk of the baby being born smaller than expected.
Regular, heavy use makes it difficult to learn and concentrate. Some people begin to feel tired all the time and can't seem to get motivated.
Some users may want to buy strong herbal cannabis to get ‘a bigger high’ but unpleasant reactions can be more powerful when you use strong cannabis, and it is possible that using strong cannabis repeatedly could lead in time to more users experiencing harmful effects such as dependence or being more at risk of developing the mental health effects.
This is from Frank. All of these risks are very uncommon, and are very mild effects. Basically, the worst thing in a spliff is the tobacco mate. Nothing to worry about smoking the occasional doobey.