304 CHAPTER 7
Neural Communication: Serotonin
OCD appears to arise in large part because brain circuits don’t operate normally,
but why don’t they? One reason may be that people with OCD have too little of the
neurotransmitter serotonin, which allows unusual brain activity to occur (Mundo
et al., 2000). And, in fact, medications that increase the effects of serotonin (such
as Prozac), often by preventing reuptake of this neurotransmitter at the syn-
apse (see Chapter 6), can help to treat OCD symptoms (Greenberg, Altemus, &
Murphy, 1997; Micallef & Blin, 2001; Thomsen, Ebbesen, & Persson, 2001).
However, in spite of the effi cacy of such medication, several studies have not been
able to document that patients with OCD have abnormally low amounts of sero-
tonin (Delgado & Moreno, 1998; Insel & Winslow, 1990). Drugs that increase
the effects of serotonin may affect the symptoms of OCD indirectly, perhaps by
decreasing activity in the neural loop that involves the frontal cortex and the basal
ganglia (Saxena & Rauch, 2000).
In addition, it is possible that different varieties of OCD arise for different rea-
sons. For example, patients who need to wash their hands repeatedly may have too
little serotonin, whereas patients who have intense ordering obsessions may have
had brain damage (Pigott, 1996). Moreover, there is a hint that different mechanisms
may cause early-onset OCD (which develops before age 10) and later-onset OCD,
as early-onset OCD responds less well to drugs that affect serotonin (Erzegovesi
et al., 2001; Rosario-Campos et al., 2001).Genetics
Twin studies have shown that if one monozygotic (identical) twin has OCD,
the other is very likely (65%) to have it. As should be expected if this high rate
refl ects common genes, the rate is lower (only 15%) for dizygotic twins (Pauls,
Raymond, & Robertson, 1991). Moreover, as you would expect from the results of
the twin studies, OCD is more common among relatives of OCD patients (10.3%
of whom also have OCD) than among relatives of control participants (of whom
only 2% also have OCD) (Pauls et al., 1995).
However, although family studies have documented a genetic contribution to
OCD, the link is neither simple nor straightforward: Members of the family of a
person with OCD are more likely than other people to have an anxiety disorder,
but that disorder need not be OCD specifi cally (Black et al., 1992; Smoller, Finn, &
White, 2000; Torgersen, 1983).
Author Emily Colas, who has OCD, recounts her mother’s struggle with symp-
toms of the disorder:
I used to get frustrated at bedtime. My mother would sit on the edge of my bed, tuck
me in, and kiss me good-night. Then she’d walk to the door and with her middle fi nger
fl ick the light switch off. The hall light was on so I could see mom standing there a few
minutes later still stroking the switch that was clearly by that time down. I’d yell “It’s
off!” to get her out of my room. She’d look back at me and then turn her head away,
silently shut my door, and leave. Fifteen years later she explained to me that she knew
the light was in fact off, but felt compelled to keep fl icking the switch, in multiples of
four, until it felt “right.”
(Colas, 1998, p. 31)
When many people fi rst learn about OCD, they recognize tendencies they’ve noticed
in themselves. If you’ve had this reaction while reading this section, you shouldn’t
worry: OCD may refl ect extreme functioning of brain systems that function the same
way in each of us to produce milder forms of such thinking. According to this view,
OCD is not a qualitatively distinct disorder, with brain systems producing abnormal
types of outputs (the way hallucinations may arise in some psychotic disorders), but
rather is just one end of a continuum—with “normal” anchoring the other end. In
fact, researchers found that the relatives of OCD patients were more likely than con-
trols to have both OCD and OCD-like symptoms that were subclinical(not severe
enough to qualify as the disorder) (Pauls et al., 1995). With subclinical symptoms,
the brain produces the same kinds of thoughts, impulses, and images as found in
OCD, but not frequently or strongly enough to disrupt daily life.Soccer star David Beckham suffers from OCD. His
symptoms focus on ordering: “I have to have
everything in a straight line or everything has to
be in pairs.... I’ll go into a hotel room. Before I
can relax I have to move all the leafl ets and all the
books and put them in a drawer. Everything has to
be perfect.” (Dolan, 2006).AP Photo/Matt Dunham