Table 3.

Individual SCOPI Items Rated Higher by Expansion-Positive Than by Expansion-Negative Participants (total N = 408)

SCOPI Itema	Expansion-Negative Groupb (N= 108) SD	Expansion-Positive Groupc (N= 300) SD	t Statistic	p Value
Obsessive Checking
1. Even when I do something very carefully, I worry that it is not quite right	2.37 (1.23)	2.74 (1.32)	2.55	<0.5
4. I sometimes am troubled by unpleasant thoughts that occur over and over again	1.54 (0.88)	1.90 (1.14)	3.42	<0.001
8. I spend a lot of time checking things over and over again	1.74 (0.93)	1.98 (1.10)	2.15	<.05
28. I am often plagued by the nagging doubt that I’ve failed to do something important	2.02 (0.97)	2.34 (1.16)	2.8	<0.01
31. I sometimes find that I cannot get rid of unpleasant thoughts that have popped into my mind	1.61 (0.85)	1.96 (1.18)	3.28	<.005
45. No matter how many times I check things over, I can’t help wondering whether I have done everything correctly	1.81 (0.91)	2.09 (1.13)	2.6	<.01
Obsessive cleanliness
2. I worry a lot about germs	1.64 (0.89)	1.88 (1.12)	2.28	<.05
Pathological impulses
5. I occasionally get a sudden impulse to do something violent or destructive	1.17 (0.48)	1.49 (0.91)	4.65	<.0001
30. I sometimes feel the need to break things for no reason	1.18 (0.47)	1.46 (0.77)	4.57	<.0001
37. I have wondered what it would be like to tear my clothes off in public	1.17 (0.50)	1.32 (0.67)	2.47	<.05
47. I sometimes feel the sudden urge to play with fire	1.07 (0.26)	1.30 (0.61)	5.12	<.0001
Compulsive rituals
17. I have a number of different rituals that I follow in my everyday life	1.49 (0.72)	1.69 (1.00)	2.18	<.05

^aAdapted from Watson and Wu.⁵ The SCOPI is in the public domain.

^bControl group with no Huntington’s disease gene expansion.

^cIndividuals with Huntington’s disease gene expansion.

Abbreviation: SCOPI = Schedule of Compulsions, Obsessions, and Pathologic Impulses.