It can take anything up to a month for the drug to be owrking effectivly in your mum's system - there is a 'bedding in' process. Likewise, if she wishes to stop, sudden withdrawal is not good, she should cut her does by one third for two weeks, then by another third for a further two weeks, and finally to one third every other day for two weeks, and extend the gap from there. If your mum misses a dose, tell her on no account to 'double up' the next day - this will throw her system out of synch, Advise her to resume the following day as normal, and accept that she may experience a mood 'dip' for a day or so while the dosage rights itself. As my learned friend advises, modern antidepressants are far morer sophisticated than the ones used years ago, so side effects are minimal, and adiciton is almost unheard of, especially at the relativly low dosage rate your mum is taking - she should be fine.