How much of an effect does zoloft have on caffeine consumption? is it always true that it increases the effect of the caffeine?

No: It is generally safe to have coffee while taking sertraline. However, if you are taking sertraline for anxiety or panic attacks, you may find that the caffeine in coffee makes you feel more anxious or makes your symptoms worse.

No effect: There is no substantial evidence in humans of caffeine and Zoloft affecting one another. The only thing to consider is that caffeine may worsen anxiousness in people with anxiety disorders. And that’s not because the two substances interact, but rather the direct effect of caffeine on anxiety itself.