What is the defence argument in a personal injury action for depression and chronic pain?

Relying on such authorities as Chanakos v. Bruce, [1997] B.C.J. No. 750 (S.C.), the defence says the plaintiff has failed to prove on a balance of probabilities that the plaintiff’s depression and chronic pain were caused by the accident. Rather the defence says that if the plaintiff suffered any injury as a result of the accident it was limited to a soft tissue injury, which was largely resolved by September 2005 and fully resolved by the time he returned to work in late 2007, with no relapse over a period of a year until December 2008 when he decided to quit work. The defence says that any ongoing symptoms are not the result of the accident but rather were caused by the plaintiff’s pre-existing psychological illness.