Tribunal of Commissioners 25 November 2005
Case Nos CDLA/2879/2004 and CDLA/2899/2004
physical symptoms or manifestations of a medical condition (whether that condition be physical or mental), it is necessary for him to show an identifiable physical cause for those symptoms or manifestations to satisfy the conditions for entitlement to higher rate mobility component of DLA under section 72(1)(a) of the 1992 Act and regulation 12 of the 1991 Regulations.
102.Our conclusion as to the effect of Harrison means that guidance is necessary, for the benefit of the new tribunal in Mr B’s case and to decision makers and appeal tribunals generally, in relation to issues concerning the proper approach to causation, and in particular issues which arise where a claimant’s inability or virtual inability to walk has both physical and mental causes. For example, commonly a claimant has some physical disorder (e.g. a disc problem), but owing to psychological problems (or “psychogenic overlay”) experiences physical symptoms to a substantially greater extent than would have been expected as a result of the physical disorder alone.
103.A number of potential issues arise.
(i)If the psychological condition is itself a direct result of a continuing physical condition, it would seem logical that the claimant’s virtual ability to walk should be found to be a consequence of his physical condition as a whole. However, is that also the case where the original physical cause of the psychological condition has resolved, but the psychological condition endures?
(ii)What if the psychological disorder arose independently (i.e. was not caused by the physical condition)? Is it then necessary, in determining whether the claimant’s inability or virtual inability to walk has a physical cause, to attempt to strip out that part of the walking difficulty which results from the psychological disorder, and if so how?
(iii)Perhaps even more problematically, what is the position where the psychological condition was partly a result of the physical condition and partly of independent origin (often the case when a psychologically fragile person suffers from a physical condition)?
104.These issues raise the more general question of what test should be applied in determining whether the inability or virtual inability to walk has a physical cause. Neither section 73 of the 1992 Act nor regulation 12(1)(a) of the 1991 Regulations supplies any obvious guidance, and neither is Harrison of any assistance.
105.Before us, there was considerable debate about the application of the traditional “but for” test for factual causation. Such a test would mean that, in order to succeed, it is necessary and sufficient for the claimant to show that he has (or possibly once had) a physical disorder but for which he would not have been unable or virtually unable to walk. Fairness and common sense would suggest that such a test may need to be modified in at least the (admittedly unusual) situation where the claimant has a physical and a mental disorder, each of which on its own would have caused him to be virtually unable to walk. A claim for the higher rate of the mobility component should not fail merely because he would in any event have been virtually unable to walk by reason of his psychological condition. More importantly, however, the test would involve the difficulty of attempting to determine whether the claimant would have been virtually unable to walk had he not had the physical