Attention Deficit/Hyperactivity Disorder
Attention Deficit/Hyperactivity Disorder (AD/HD) is comprised of problems with sustained attention distractibility impulse control and hyperactivity (APA, 1994; Barkley, 1990). It is estimated that approximately 3-7 per cent of school-age children have this disorder, but most estimates are towards the higher end of the range (Szatmari, 1992, cited in Barkley, 1997b).
AD/HD is believed to show itself first in early childhood, usually between the ages of 3 and 7, although it can appear well before or after this typical age period (Barkley, 1982, 1997a, 1998). It occurs much more commonly among boys than among girls; ratios range from 2 : 1 to 5 : 1 (Accardo et al., 1990; Bhatia et al., 1991; Kanbayashi et al., 1994).
Although first described by Still (1902), it was first included as `Attention Deficit Disorder' (ADD) in D.S.M. III (APA, 1980). In D.S.M. IV (APA, 1994) there are nine criteria for Inattentiveness, and nine for Hyperactivity/Impulsiveness, leading to possible diagnoses of AD/HD combined type, or AD/HD predominantly Inattentive type, or AD/HD predominantly Hyperactive/ Impulsive type. People who suffer from six or more items from each of the two lists in at least two different conditions (e.g. school and home) are designated AD/HD combined type (APA, 1994), which in this study is referred to simply as `AD/HD' (see Appendix 1).
Within the model devised by Barkley, it is argued that the data suggest that AD/HD is specifically concerned with a deficit in the development of behavioral inhibition (Barkley, 1997a, b; Pennington and Ozonoff, 1996) and that it interferes with self-regulation and the organisation of future-directed behaviour (Barkley, 1997a, b, 1998). It also seems that AD/HD creates insensitivity to general response consequences, rather than being primarily a disturbance in attention, as the name suggests (Barkley, 1989, 1997a, b), causing problems with motivation generally. It was found, for example, that under continual reward conditions AD/HD children usually blend in with 'normal' children on general tasks, but under conditions of partial or no reward the children with AD/HD decline significantly in performance (Douglas and Parry, 1983, 1994, Parry and Douglas, 1983, both cited in Barkley, 1997b).
The disorder appears to be fairly stable throughout development, and is thought to persist into adolescence in up to 80 per cent of clinically diagnosed cases (August et al., 1983; Barkley, 1990, 1997a, 1998), and into adulthood in as many as 66 per cent of those cases (Mannuzza et al., 1993). The actual prevalence of AD/HD in adults is unknown because at present no epidemiological studies have been carried out to evaluate `residual AD/HD' (blender, 1995). However, in a ten-year follow-up study, Weiss and Hechtman (1993) found that half the original group continued to have significant problems of the same kind as they had had before, putting the population estimate of AD/HD adults at about 3-7 per cent overall. Follow-up studies do, however, have many methodological problems, particularly the loss of many participants for reasons such as their having had a serious accident or being institutionalised. Most of the reasons are attributed to Antisocial Personality Disorder (blender, 1995), which is expected to develop in one AD/HD child in six by the time it reaches adulthood (Barkley, 1997a, 1998).
There are different ways of diagnosing AD/HD. The most common approach is the use of a categorical classificatory system such as D.S.M. (e.g. APA, 1986, 1994). This system can be criticised because, for any of the D.S.M. classifications, the required number of symptoms indicates the existence of the syndrome but failure to meet the cut-off point by even one criterion means that the condition is regarded as absent. Empirical findings to date suggest that neither the LC.D. nor D.S.M. IV has yet formulated a satisfactory scheme (e. …