Clinical Psychology

variables are perfectly and positively related. Anrof

• 1.00 indicates a perfect negative relationship. The
  rof +.76 from the data of Table 4-2 signifies a high
  but less than perfect relationship.
  Ascatterplotof the data points for the two vari-
  ables from Table 4-2 is shown in Figure 4-1. Each
  data point corresponds to one participant’s scores on
  both anxiety and control. For example, the data
  point nearest the lower left corner represents Ralph’s
  scores of 4 on anxiety and 2 on control. Figure 4-2
  presents scatterplots for several correlations.

The more nearly perfect a relationship, the

closer to a straight line the data points will be. As

rapproaches zero (no relationship), the data points

are scattered in a nearly random fashion throughout

the scatterplot.

The Question of Causality. As noted previously

in the case of epidemiological research, correla-

tional methods cannot answer the question of

cause and effect. No matter how logical it may

appear, we cannot, on the basis of a correlation

T A B L E 4-1 Lifetime and 12-month Prevalence of DSM-IV Psychological Disorders
and Median Age of Onset

Lifetime 12-Month Age of Onset

Anxiety Disorders
Panic Disorder 4.7 2.7 24
Agoraphobia without panic 1.4 0.8 20
Specific Phobia 12.5 8.7 7
Social Phobia 12.1 6.8 13
Generalized Anxiety Disorder 5.7 3.1 31
Posttraumatic Stress Disorder 6.8 3.5 23
Obsessive-compulsive Disorder 1.6 1.0 19
Separation Anxiety Disorder 5.2 0.9 7
Any Anxiety Disorder 28.8 18.1 11

Mood Disorder
Major Depressive Disorder 16.6 6.7 32
Dysthymia 2.5 1.5 31
Bipolar I and II disorders 3.9 2.6 25
Any Mood Disorder 20.8 9.5 30

Impulse-Control Disorders
Oppositional Defiant Disorder 8.5 1.0 13
Conduct Disorder 9.5 1.0 13
Attention-deficit/Hyperactivity Disorder 8.1 4.1 7
Intermittent Explosive Disorder 5.2 2.6 15
Any Impulse-Control Disorder 24.8 8.9 11

Substance Use Disorders
Alcohol Abuse 13.2 3.1 21
Alcohol Dependence 5.4 1.3 23
Drug Abuse 7.9 1.4 19
Drug Dependence 3.0 0.4 21
Any Substance Use Disorder 14.6 3.8 20
Any DSM-IV Disorder 46.4 26.2 14

SOURCE:Lifetime and 12-month ratesrepresent the proportion of United States residents with the psychological disorder.
Adapted from: Kessler, Berglund et al. (2005); Kessler, Chiu et al. (2005).

102 CHAPTER 4