Sometimes people use cannabis (and other drugs) in the belief that it will help them cope better with their problems and feelings. Using cannabis in this way, however, can cause those problems to become more severe and difficult to manage in the long-term.

The effects of cannabis on mental health

Cannabis use can have a range of mental health effects on people. Although rare, sometimes it can produce anxiety and panic in a person after a single use. In high doses, cannabis can cause confusion, thought disorder and hallucinations.

Some people are more vulnerable than others to experiencing these negative effects of cannabis, especially those with a personal or family history of mental illness. People who start using cannabis young, or use cannabis heavily, are more likely to experience psychotic disorders and depression later in life.

Doctors prescribe medication for depression, psychosis, bipolar affective disorder or schizophrenia to bring relief from the unpleasant symptoms that a patient may be experiencing. If that person continues to use cannabis while taking prescribed medications, unknown reactions can occur, which may make their condition worse. It also makes it very difficult for their doctor to prescribe the right drug at the right dose to improve their symptoms, as well as increasing the risk of non- compliance with medication regimes.

Mixing cannabis with antidepressant medication

People who have been diagnosed with depression can be prescribed antidepressants. There are four main groups of antidepressants:

• Tricyclics – Nortryptyline (Allegron), Clomipramine (Anafranil), Amitriptyline (Tryptanol), Imipramine (Tofrinal), Dothiepin (Prothiaden)
• Selective Serotonin Reuptake Inhibitors (SSRIs) - Sertraline (Zoloft), Paroxetine (Aropax), Citalopram (Cipramil), Fluoxetine (Prozac), Fluvoxamin (Luvox)
• Monoamine Oxidase Inhibitors (MAOIs) – Moclobemide (Aurorix), Phenelzine (Nardil)
• Newer antidepressants – Mirtazapine (Avanza), Venlafaxine (Efexor) and Reboxetine (Edronax)

Very little research has been conducted on the effects of using cannabis while taking prescribed antidepressant medication. The side-effects of antidepressants can be similar to those produced by cannabis use however, and these include the following:

• abnormally fast heartbeat (tachycardia)
• dizziness
• anxiety
• panic
• drowsiness
• nausea
• confusion

The danger of using cannabis while on antidepressants is that it can intensify any or all of these side effects and make a person feel worse.

Mixing cannabis with antipsychotic medication

Antipsychotic medication is prescribed for people who have had psychotic episodes and have been diagnosed with schizophrenia. Common antipsychotic medications used in Australia are:

• Antipsychotic Medications (older medications) – Chlorpromazine HCl (Thorazine), Thioridazine HCl (Mellaril), Haloperidol (Haldol)
• Atypical Antipsychotic Medications (newer medications) – Olanzapine (Zyprexa), Resperidone (Risperdal), Clozapine (Clozaril), Quetiapine (Seroquel)

Antipsychotic medications are most effective in treating the hallucinations and delusions associated with schizophrenia and other psychotic disorders, however they may not help with other symptoms such as motivation and emotional responsiveness. Because of this, people with schizophrenia can experience depression which may also need to be treated. All these symptoms are made worse if cannabis is being used.

Research suggests that counselling can greatly improve the chances of a person giving up or cutting down their cannabis use while taking medication.

While there is very little research on the effects of the combination of cannabis and antipsychotic medications, there is evidence that suggests that those people prescribed Clozopine experience less craving for cannabis than those who are prescribed Resperidone or Quetiapine. Further research into this area is being conducted.

Getting help

If you use cannabis regularly and take prescribed medications, or know someone who does, the following things may help:

• make sure the prescribing doctor is aware of the cannabis use and how much is being used
• see a specialised counsellor – it greatly improves the chances of decreasing or stopping cannabis use while taking medication
• give the medication a chance – it can take up to six weeks for antidepressant and antipsychotic medications to take effect
• be aware that if cannabis is taken with antidepressants, it can produce similar side-effects and intensify reactions, such as rapid heartbeat, dizziness, anxiety, nausea and sweating
• do not take cannabis with tricyclic antidepressants because this increases the risk of rapid heartbeat and other side-effects such as confusion, restlessness, mood swings and hallucinations
• do not take cannabis with MAOI antidepressants as it is thought to affect the way the medicine works
• do not use cannabis with newer antidepressants as there is very little published research about possible reactions
• there has been limited research on taking cannabis with SSRI antidepressants. However, the limited information available suggests that SSRIs may be a safer choice of antidepressant if you use cannabis. Make sure you speak to your doctor for further information
• avoid using cannabis if you are prescribed antipsychotic medication
• if there are any problems experienced while being on medication and using cannabis see a doctor or health care professional

Remember, the medications are prescribed to make people feel better. Using cannabis as well, will make the symptoms worse and the medications less effective.