THC does, but Cannabis contains CBD as well, which does the opposite.
There's some lab that uses CBD to help with mental illnesses in some country. Do a google search if you're interested.
But here's a pdf on CBD: http://www.scielo.br/pdf/bjmbr/v39n4/6164.pdf
A high dose of ∆9-tetrahydrocannabinol, the main Cannabis sativa (cannabis) component, induces anxiety and psychotic-like symptoms in healthy volunteers. These effects of ∆9-tetrahydrocannabinol are significantly reduced by cannabidiol (CBD), a cannabis constituent which is devoid of the typical effects of the plant. This observation led us to suspect that CBD could have anxiolytic and/or antipsychotic actions...In conclusion, results from pre-clinical and clinical studies suggest that CBD is an effective, safe and well-tolerated alternative treatment for schizophrenic patients. Future trials of this cannabinoid in other psychotic conditions such as bipolar disorder (50) and comparative studies of its antipsychotic effects with those produced by clozapine in schizophrenic patients are clearly needed
All the methods, results etc. are in the pdf and worth reading. Don't take my word for it! ermm