When I was designing the diver panic study back in 2000, I reviewed the literature and contacted all the pharmaceutical companies that supplied psychiatric medications in the USA. None of them had any data on psychiatric medications in the hyperbaric (diving) environment and I have not seen anything since then. It is vey unlikely that any of them will ever fund such a study. I've asked. The survey of over 12,000 divers that my wife and I did in 2000 showed no significant increased relative risk of panic for the divers on antidepressant medications.
In 2000 the standards for medical fitness for recreational scuba diving prohibited scuba diving for people who were taking psychtropic medications. When I called around and asked the various experts at DAN and other published dive medicine physicians about the rule, they thought it came from the old days of Thorazine and tricyclic antidepressant medications which were notorious for lots of side effects like heavy sedation and dry mouth and the list goes on and on, which could have been a problem while diving.
However, the fitness standards were changed a few years ago (I think in 2002) to reflect the reduced side effects and more wide-spread use of the newer medications. I discussed this in my presentation in September 2007 in Johannesburg at the SAUHMA Refresher course in Underwater Medicine 2007. You can download a pdf file of the talk from
www.DivePsych.com : "Anxiety, Panic and Psychiatric Problems in Divers". The organizers had asked me to address the question of antidepressant and other psych medications in divers.
I was surprised that some of the dive medicine examiners in attendance were recommending conditional depth limits for divers on these medications in the absence of any objective evidence. Certainly, if a diver is already having side effects that impair alertness or judgement on land, then they would likely still have them in the hyperbaric environment and would be advised to not dive or even to drive a motor vehicle or to operate dangerous machinery. However, I have not seen any evidence that these medications cause any more problems underwater than on land.
A diver's judgement can be impaired by nitrogen narcosis either with or without a psychotropic medication on board. It is theoretically possble that a medication that causes sedation on land could exaggerate the impairment from the nitrogen narcosis, just as would alcohol or cannabis. I am not aware of any published reports at this time.
The one psych medication that can be a problem in scuba divers is lithium carbonate because of toxicity if the diver becomes very dehydrated while sweating from baking in the sun on the beach or on a boat in a dry suit or thick wetsuit. That could be quite dangerous and potentially lethal.
Over the years none of my patients have reported any problems while diving on psychiatric medications from the medications. I have accummulated a significant survey database of divers over the past few years and can not recall any reports of problems despite some having been on multiple strong medications. That is anecdotal data, but there are also no published controlled studies upon which to make an evidence based decision. As DocVikingo pointed out, the bigger concern is any limitation from the illness for which the medications have been prescribed.
On the other hand, quite a few divers have told me that scuba diving is one of the main pleasures they have in life and that they feel more at peace underwater than anywhere else. I think it is a great activity for depressed patients, close to therapeutic. The folks over at DAN have told me there are few if any documented cases of suicide by scuba diving.
As far as the SNRI antidepressant Cymbalta goes, I am not aware of anything about that particular medication that would be uniquely worsened by the hyperbaric environment while scuba diving. People can respond differently to medications, so a scuba diver is advised to consult his physician any time he/she uses a medication.
As Doc says, "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."