Smoking marijuana can leave a lasting impact on the brain, a new study says. Reuters

The New Year for Colorado will bring in a 'major' reform that will see an ease in the recreational use of marijuana. As reforms kick in, Colorado will start selling marijuana for recreational use through retail stores with valid permit starting 1 January.

The first batch of licenses were given out to owners of cannabis dispensaries in Denver. Earlier in 2012, Colorado had voted for a new law that allowed the production and sale of medical marijuana for recreational use. In the first round, 42 licenses have been issued.

There are more than 500 medical marijuana dispensaries already in the state, and as per new law only these existing marijuana stores outlets will be able to apply for license.

The dispensaries will have to get recreational sale license, besides the local license; the first batch of which was distributed in Denver.

As per the new rule, any resident in Colorado - who is 21 or above - will be able to legally buy 'cannabis' up to one ounce, and grow up to six marijuana plants for personal use. However, the conflict is that the federal government still considers marijuana an illegal substance. There are still areas in Colorado that have voted against the relaxing of the cannabis rule, which does bring in some local conflicts.

Besides, driving 'high' will also be monitored. There is a new law specifically to cover the offence of driving under the influence of drugs, that sets a limit of 5 nanograms of THC (Tetrahydrocannabinol), the main mind-altering ingredient found in the Cannabis.

Also, reportedly employers can still fire an employee, if he/she is found to be high at work.