anxiety
"I have been on Pristiq for a few years now at different dosages:  
50mg - Positives: loss of appetite, weight loss and feeling great. Negatives:  your body gets used to the medicine until it seemingly no longer works.  The side effects of loss of appetite, sleep patterns etc. do stop after about 3 weeks.
100mg - Feel good, appetite normal. Negatives:  You will feel drowsy to exhausted.  Again my body seems to get immune to the dosage.
200mg - Postive:  Feel good and normal energy levels. Negative:  Major Weight gain, constipation and you feel the cold/hot flushes. These side effects don't wear of with time at this dosage."