What is the long term complications of taking an anti-depressant? serious question?

Although these drugs increase the levels of NE and 5-HT in your neural synapses, there is no direct evidence that deficient NE and 5-HT cause depression in the first place. It has since been found that these type of drugs actually affect the morphology of your brain, and a popularised theory (which is backed by a myriad of histological evidence) is that these kinds of drugs promote neurogenesis in the hippocampus - an area of the brain involved in memory and learning. Impaired neurogenesis has been linked to depression. So in answer to your question, yes it is likely that these drugs are going to have a long term effect on the structure of your brain. But as for causing complications, I'm no expert in clinical medicine but since NE and 5-HT aren't a direct constituent of the brain reward circuitry I doubt you can get addicted to them in the same way that people get addicted to psychostimulants. Other changes to NE and 5-HT synapses I'm guessing are likely to be short term and will reverse when you come off of the drugs.