posted on Nov, 15 2016 @ 07:55 PM
I think it's partly directly related to metabolism, as well as the effects of the drug in respect of affecting one's feeling of being energetic,
hungry and otherwise. For example, dopamine-related drugs (such as amphetamine) might make somebody feel like they have more energy than normal, and
therefore may be more physically active whilst on a course of related drugs. As for serotonin-related drugs, they can work either way and it might
depend on the type - so far as an MAOI goes, higher doses tend to cause the drug to have more of a suppressing effect, although high doses of this
type of drug would be a last-line option in severe cases of depression. Also, some drugs can physically suppress the system by their nature, such as
tranquillisers and anaesthetics, which could by all means suppress metabolic functions.
The main things to consider are...
How it affects one's satiety
How it affects one's feeling of having energy
How the drug affects metabolism in its own right
How it affects saliva - too little could make eating painful
How much activity the person undertakes whilst on the drug
Suffice to say, if a person is more active than normal and they eat less, they will probably lose weight. If the drug makes them feel less energetic
and they are thus less active, but at the same time the drug does not suppress their appetite so they eat well during the course, then they are
probably storing more energy than they require.
It's also worth bearing in mind that if a person is grossly under- or overweight in the first place, it could be a reason as to why they ended up on
anti-depressants. In that case, you could think the drug causes it but in reality it was already a problem.
Personally, I think there are too many factors to really say whether or not a particular drug will directly affect the patient's weight. Some specific
drugs or types may specifically affect weight, but anti-depressants probably depend mostly on the individual's physical condition and their lifestyle.