Results highlight the need for early and effective intervention of both episodic mood disorder and inter-episode interpersonal dysfunction inherent to the personality disorders. Future maintenance treatment trials are needed to clarify the relationship between episodic mood disorder and personality function over time.

1 At 37°C in 0.1 M NaCl the pKa of hyoscine (10 mM) is 7.53; the non-protonated form has about one-tenth of the affinity (log K = 8.58) of the protonated form (log K = 9.58) for muscarine-sensitive receptors of the guinea-pig ileum at 37°C.2 In the same conditions the pKa of hyoscine N-oxide is 5.78 and the non-protonated form is inactive on the ileum whereas the protonated form is highly active with log K estimated to be 9.9, at least as active as hyoscine methobromide (log K = 9.85).3 Hyoscine methobromide appears to occupy less space in water than atropine methobromide; hyoscine hydrochloride occupies less space than hyoscyamine hydrochloride: the non-protonated forms are slightly bigger. Hyoscine N-oxide hydrobromide is slightly smaller than hyoscine methobromide but the removal of the proton is accompanied by a reduction in volume, such as is seen with other zwitterions. 4 These differences in volume indicate a reduction in entropy on solution which may allow a greater increase in entropy on binding to receptors and hence greater affinity. The higher activity of hyoscine itself could also be due to the presence of the N-methyl group in the axial position, rather than equatorial as in hyoscyamine or atropine.5 The different position of the N-methyl group may partly explain why the pKa of hyoscine is 2 units lower than that of hyoscyamine or atropine. It is also probable that the unionized form of hyoscine is stabilized by hydration. 6 Although hyoscine N-oxide is only weakly active at pH 7.6, it is present in a highly active form in the acid environment of the stomach and so might be expected to act selectively at this site.

Much of the risk assessment literature has focused on the predictive validity of risk assessment tools. However, these tools often comprise a list of risk factors that are themselves complex constructs, and focusing on the quality of measurement of individual risk factors may improve the predictive validity of the tools. The present study illustrates this concern using the Antisocial Features and Aggression scales of the Personality Assessment Inventory (Morey, 1991). In a sample of 1,545 prison inmates and offenders undergoing treatment for substance abuse (85% male), we evaluated (a) the factorial validity of the ANT and AGG scales, (b) the utility of original ANT and AGG scales and newly derived ANT and AGG scales for predicting antisocial outcomes (recidivism and institutional infractions), and (c) whether items with a stronger relationship to the underlying constructs (higher factor loadings) were in turn more strongly related to antisocial outcomes. Confirmatory factor analyses (CFAs) indicated that ANT and AGG items were not structured optimally in these data in terms of correspondence to the subscale structure identified in the PAI manual. Exploratory factor analyses were conducted on a random split-half of the sample to derive optimized alternative factor structures, and cross-validated in the second split-half using CFA. Four-factor models emerged for both the ANT and AGG scales, and, as predicted, the size of item factor loadings was associated with the strength with which items were associated with institutional infractions and community recidivism. This suggests that the quality by which a construct is measured is associated with its predictive strength. Implications for risk assessment are discussed.

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