this population implies that targetting this group alone will not make a large impact on suicide in the general population. Note also that the last three rows, indicating number of psychiatric symptoms, have a decreasing relationship with both PAR and PPE. This indicates that broadening the target group can lead to a higher population effect than a strategy relying on a very high risk group.

When population-based strategies are considered, a larger impact can be effected. This can be illustrated with an example for early risk interventions such as prevention of aggression and conduct disorder, and substance abuse. In this illustration, it is estimated that the early risk factor (whichever example might be chosen) has 15 percent prevalence in the population (similar to early aggressive behavior). Because the risk factor has relatively high prevalence, its relative risk is rather modest (a value of 2 is selected for analysis). Two situations are considered for early risk interventions (see Table 8-4). The first is based on the highly optimistic assumption that a broad-based prevention program has completely successful impact on the high-risk group but produces only a 5 percent decrease in risk among the low-risk group. In this case, the overall reduction in risk is 34 percent. A second alternative is to assume 50 percent impact in the high-risk group and no impact in the low-risk group. This still produces a respectable 15 percent reduction in overall risk for suicide.

These strategies compare quite favorably with the impact of strategies involving crisis telephone lines. Crisis lines are now being used by about 2 percent of the population. Various technologies currently exist to improve participation in prevention programs and through higher utilization increase hotline effectiveness; the analysis here uses 5 percent. Even with the assumption of a very liberal relative risk of 2.5–10 for

TABLE 8-4 PAR and PPE for Alternative Population-Based Prevention Programs

 

p(X)

RR

PAR

IE(X)

IE(Xc)

PPE

Early Risk

15.00%

2

13%

100%

5%

34%

 

15.00%

2

13%

50%

0%

15%

Crisis Line

2.00%

2.5

3%

10%

0%

1%

 

5.00%

2.5

7%

10%

0%

1%

 

2.00%

10

15%

10%

0%

2%

 

5.00%

10

31%

10%

0%

5%

Gatekeeper

10.00%

2.5

13%

10%

0%

3%

 

20.00%

2.5

23%

20%

0%

10%

 

SOURCE: Brown, 2001.



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