OBJECTIVE : An association between the Leucine-rich repeat trans membrane neuronal 1 gene (LRRTM1),
schizophrenia/schizoaffective disorder and handedness was recently claimed to be
established. This study aimed to test the hypothesis that Afrikaner patients with
schizophrenia/schizoaffective disorder are more non-right handed than their non-affected
first-degree relatives and that of two separate control groups. The association between
handedness, gender and age at onset of illness in the patients group was also determined.
METHOD : Two cross-sectional studies were carried out, which compared the handedness of a group of
100 (30 females and 70 males) Afrikaner patients with schizophrenia/schizoaffective disorder, their non-affected first-degree relatives, and two separate control groups.
Handedness was determined by the Edinburg Handedness Inventory (EHI).
Patients were found to be more right-handed than expected with only 17 out of 100 being
non-right-handed compared to 11 out of 100 non-affected relatives; 36 out of 100 students
and 75 out of 500 non-affected Afrikaner participants. The students were significantly more
non-right handed than the patient and family groups but no difference in handedness was
found when comparing the patients, family members and 500 participant control group.
There was no significant difference between age at onset of illness and handedness. A
significant association between female gender and non-right handedness in the patient
group was found but no gender difference in the family and student groups. A highly
significant association was found between the male gender of the patients and student
control group regarding handedness. A significant difference was found between the median
EHI raw scores of the patients and the family members. The median EHI raw scores of the
patients were significantly lower than their paired family members.
CONCLUTION : The study failed to prove a leftward shift of handedness in the patients with Schizophrenia
and Schizoaffective disorder in the Afrikaner Founder population. Whether or not LRRTM1 is
indeed the genetic basis of handedness, remains unclear.