Dopamine and serotonin are raised by l-theanine found in green tea. Safe to drink that as well as take sertraline 200mg or cause serotonin syndrome?

Green tea. If simply drinking the beverage green tea, the amount of l-theanine will not be high enough to increase serotonin to the point of serotonin syndrome. Theanine in supplement form has increased synthesis of neurotransmitters (including serotonin) in rats, but these findings don't automatically transfer to humans. If only drinking the tea (not taking the supplement) you're probably fine.