Why are marijuana laws so harsh?

My best answer is that the prolonged use of marijuana leaves huge psychological effects, it can lead to you taking 'harder' drugs and it generally effect those that surround you as well through mood changes. You're more likely to become violent and from personal experience it is not nice being around someone you know is using marijuana and it leads to a breakdown in trust.You're not just damaging your own body, you're damaging the relationships and your mental health, as the effects can become known years after you stop using marijuana or just the occasional 'drag'. Also the potential for finding employment and the initiative to find employment and the drive to go to work plummets when you starts using it, You suddenly can't be bothered anymore... Just don't do it, so you can't be caught, so you won't go to jail or have a record that will affect you later in life when you will live to regret the decision.