Marijuana can indeed have long lasting effects even after it has been washed out of your body. Usually u can trace cannabis in urine test for upto 4 weeks from last use.
One of the effects of Cannabis is to generate euphoria since it acts on the same tracts in your brain meant to generate pleasure (known as reward pathway). During this action it can sometimes alter homeostasis (working balance) of the neuro chemicals internally present that are meant to this function and this can generate various symptoms ranging from simple prolonged euphoria, impaired concentration, motivation, blunting to emotions to upto florid Psychotic symptoms with thoughts and perception abnormalities.
Each person reacts to the
THC differently depending upon his/her genetic makeup and other environmental factors.
It is like sugar which has different meaning for a diabetic vs non-diabetic.
However in case you are experiencing some prolonged effects which could be pathological thereby affecting your functioning
and/or
if you have even remote family history of some mental health issues
Then make sure that in future you avoid Cannabis like a
plague.
I hope you find this information useful