How long does it take at Celexa (citalopram) to have an effect?

Antidepressants usually take 2 to 4 weeks to take effect. The maximum effect is usually reached after 8 to 12 weeks of treatment. Citalopram may be less stimulating than sertraline, but this depends a lot on the person taking it. The stimulating effect you complained about with sertraline should disappear quickly, usually within a few days.