You may want to consult the Apr/May '03 issue of "Alert Diver" magazine as it contains a piece on diving & depression. I am doing a more detailed follow up article on the subject that is scheduled to appear in the Jun/Jul '03 edition. It focuses more directly on the actual decision making process involved in fitness to dive while on SSRIs like citalopram (e.g., Cipramil) and other antidepressants.
If you do not get this publication, you may e-mail me and I'll give you a contact at DAN who will send you free copies of those issues.
In short, there are many considerations in diving with depression, and the possible effects of medication, although quite important, are not the only ones. The mood disorder itself can impair certain mental and physical faculties necessary for safe diving.
As regards citalopram, adverse reactions such as nausea & vomiting, insomnia, fatigue, drowsiness, dizziness, agitation, weakness & others have been reported. Understandably, the manufacturer cautions to "avoid participating in activities requiring complete mental alertness, judgment, and physical coordination - such as driving an automobile or performing hazardous tasks - until you are reasonably certain that treatment with citalopram does not affect you adversely." On the bright side, 20mg/day is at the lower end of the recommended dosage range and this should minimize side effects.
Obviously, a diver would at the least want to be confident that he was free of these before doing scuba. This means stopping diving until the medication has been given a fair trial topside. During that period, the diver should consult with a medical referee who can gather the information required to make a supportable fitness to dive decision.
Having just recently spoken with several senior physicians within the UK Sports Diving Medical Committee system, I see no reason to be unduly pessimistic about your prospects. The prevailing wisdom seems to be to decide situations such as yours based on the findings in the individual case rather than on some arbitrary & inflexible set of rules, although certain antidepressants, such as bupropion (e.g., Wellbutrin), are held as absolute contraindications to scuba due to such side effects as seizures. Hopefully, the medical referees out in the trenches will be as enlightened.
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such.
Please do let me know what the referee decides.
Best regards.
DocVikingo