The MTFS, is a developmental, longitudinal investigation of twin children that currently involves about 1,700 families. Families are recruited when the twins are either 11 or 17 years old. The twins are followed prospectively for 12 or more years. A major hypothesis of the study is that a key factor in the development of substance abuse is a predisposition to behavioral disinhibition that is genetically influenced and manifest in personality traits related to impulsivity and risk-taking behavior and psychophysiological measures reflecting poor inhibitory control. Besides examining nicotine, alcohol, and illicit drug use disorders, the MTFS is also a study of childhood psychopathology, including attention-deficit hyperactivity disorder, oppositional defiant disorder, and conduct disorder. In addition, it provides an opportunity to study the development of antisocial personality disorder, major depression, anxiety disorders, and eating disorders. For more information on this study, see Iacono and McGue (2002; Twin Research).
In the related SIBS study, adolescent adoptees, half of whom are from foreign countries (mostly Asian), are being studied along with their adoptive parents to determine how factors shared by families influence the development of substance use and related disorders. Almost 600 families have been enrolled in this study to date. Because the MTFS and SIBs studies are longitudinal, I am interested in the developmental trajectory of the disorders studied.
In both the MTFS and the SIBS projects, blood is taken from study subjects to enable the search for genes related to the psychopathology and traits under study. For twins and their parents, psychophysiological measures are used to help understand the etiology of the different psychopathological disorders we study. Some of our measures are designed to serve as endophenotypes, i.e., as markers of genetic vulnerability for the development of a particular disorder. The P300 wave of the event-related potential is one such measure. We also monitor spontaneous EEG, and are interested in the relationship between EEG oscillations and event-related potential waves. Autonomic and eye-blink startle assessments are an important aspect of our protocol which is intended to tap into the biological basis of internalizing and externalizing disorders. We have recently begun an MRI study with twins that is designed to determine how brain structure and function relate to the substance abuse outcomes we observe. Twins are optimal study subjects for such research because we can use monozygotic (identical) twins who differ in their patterns of substance use to gain insights into how drugs alter brain development.
I am also interested in the detection of deception. Most of my work in this area deals with the validity of conventionally applied lie detection techniques and their use in forensic settings. However, I am also interested in how novel techniques based on the measure of brain potentials can be used to probe the memory of criminal suspects.
