Some people with bipolar disorder who use cannabis (marijuana) claim that it eases the symptoms of depression and mania. There are many chemicals (called cannabinoids) found in cannabis but two particular ones appear to have medicinal (therapeutic) effects. These two compounds are: delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). These cannabinoids appear to have mood, anxiety, and sedative effects as well as have antipsychotic and anticonvulsant properties. This study will try to find out if these cannabinoids can be of benefit as an add-on treatment in bipolar disorder and what effects it has on thinking power and memory.