Environmental tobacco exposure (ETS) as a pathway to youth addiction

Research has shown that exposure to environmental tobacco smoke (ETS) leads to
the uptake of nicotine in the body, and a growing number of studies suggest
that this may possibly result in neuro-physiological changes in the brain and
altered psycho-behavioural responses to nicotine in never- and novice-smoking
adolescents. Psycho-behavioural responses or psycho-behavioural symptoms (PBS)
are symptoms that develop in response to nicotine dependence (e.g., tolerance
to aversive effects of nicotine, sensitization to rewarding effect of nicotine,
withdrawal symptoms after the effects of nicotine wear off). Recently it has
been shown that in never-smoking adolescents, a higher number of smokers in the
social environment is associated with self-reported PBS indicative of nicotine
dependence. In addition, exposure to ETS is associated with increased rewarding
sensations in response to the first dose of nicotine in adolescents who
recently initiated smoking. These studies indicate that exposure to ETS may
result in the development of psycho-behavioural symptoms indicative of nicotine
dependence in never-smokers and in an increased vulnerability to develop
nicotine dependence in novice smokers.
Although previous research indicates a relationship between ETS exposure and
PBS indicative of nicotine dependence in both non-smokers and novice smokers,
it has never been investigated whether ETS exposure actually precedes the
occurrence of PBS. Moreover, the potential underlying neurobiological
mechanisms through which ETS might predispose both never smokers and novice
smokers towards addiction are unknown.
Therefore, the proposed project aims to test whether PBS among adolescent
non-smokers and novice smokers are indeed the result of ETS. Furthermore, the
proposed project aims to investigate the underlying neurobiological mechanisms
through which ETS predispose adolescents towards addiction.

With this study we aim to investigate the occurrence and development of PBS
indicative of nicotine dependence in never smokers and novice smokers and the
underlying neurobiological mechanisms as a function of the level of ETS
exposure. Therefore, we specified the following main objectives:
1) To test whether ETS exposure precedes the occurrence of psycho-behavioural
symptoms (PBS) indicative of nicotine dependence.
2) To investigate the role of ETS on time period and the process in which
smoking initiation occurs and potentially progresses into more established
levels of smoking and more severe levels of PBS.
3) To investigate the association of ETS exposure with brain activation during
smoking cue-reactivity, non-drug reward sensitivity and impulse control in
never smokers by means of event-related potentials (ERPs) measured with EEG.
4) To investigate the association of ETS exposure with changes in brain
functioning over time in specific brain regions of interest (ROIs) involved in
smoking cue-reactivity, non-drug reward sensitivity and impulse control in
novice smokers using fMRI.

To determine whether ETS exposure precedes the occurrence of PBS, this study
will use Ecological Momentary Assessments (EMA) for a period of three weeks at
the start of the study. To investigate the role of ETS on the time period and
the process in which smoking initiation occurs and potentially progresses into
more established levels of smoking and PBS, this study will have a three wave
longitudinal design (1 year with six-month intervals). During both the three
waves of the longitudinal study and the EMA study, self-report questionnaires
assessing smoking patterns, dependence symptoms, and ETS exposure will be
filled out. These questionnaires provide more information on adolescents*
exposure to ETS, development of PBS, own smoking behavior, as well as smoking
behavior of their parents, siblings and friends.
To investigate the underlying neurobiological mechanisms through which ETS
predisposes adolescents towards addiction, we will use EEG measurements in
never-smoking adolescents and we will use fMRI measurements in novice smoking
adolescents at two time points, once at the start and once again one year
later. Brain activation during smoking cue-reactivity, non-drug reward
sensitivity and impulse control will be measured by means of event-related
potentials (ERPs) measured with EEG and within specific regions of interest
(ROIs) measured with fMRI. This brain activity will be related to the amount of
exposure to ETS.

There is no risk during both the EMA study and the longitudinal study as
participants will only be asked to fill out questionnaires and provide saliva
samples. Furthermore, fMRI and EEG are safe and non-invasive methods for
measuring brain activity. However, the noise and the relative confined space of
the MRI scanner may cause some level of discomfort to some subjects. The study
has no therapeutic goals; there are no benefits for the participants. The
participants in this study will be aged between 12-18 years old to
appropriately follow the initiation of smoking and potentially progresses into
more established levels of smoking and development of PBS. Overall, the
knowledge we gain through this project, as well as the risk-free nature of this
study, justifies the efforts of the participants.