Hypnosis, attention and attention deficits : perspectives from brain functions, behavioral performance and clinical applications

Background. The present thesis combines studies on hypnosis, attention, and attention deficits from various perspectives to extend our understanding of hypnosis and its applications. This thesis includes experimental and clinical research of hypnosis from the perspectives of brain functions, behavioral performance, and clinical interventions. This thesis investigated whether brain oscillations, pre-attentive auditory information processing, auditory attentional performance, and deficits of attention can be influenced by hypnosis and hypnotic suggestions. Two studies focused on highly hypnotizable healthy participants, one study compared adults with attention deficit hyperactivity disorder (ADHD) to control participants, and one investigated solely adults with ADHD. Aims. The present thesis examined: 1) whether hypnosis differs from the wake state as measured with the spectral power density of electroencephalography (EEG); 2) whether hypnosis and hypnotic suggestions can be used to influence bottom-up and/or top-down auditory attention. The former was indexed by the pre-attentive mismatch negativity (MMN) component of the auditory event-related potential (ERP). The latter was measured as the performance on a Continuous Performance Test (CPT); 3) whether hypnotherapy and hypnotic suggestions can be applied to adults with ADHD to relieve their symptoms in a long-lasting way, and to improve their attentional performance in an auditory reaction time task requiring sustained voluntary attention. Methods. The present thesis applied various methods for investigating the research aims: EEG (Studies I–II), behavioral reaction time task (Study III) and self-report measures for evaluating the follow-up results of two individual psychological treatments, hypnotherapy and cognitive behavioral therapy (CBT) in ADHD adults (Study IV). The first three studies had a similar procedural structure including four experimental conditions: 1) pre-hypnosis, 2) after a hypnotic induction (i.e., neutral hypnosis), 3) hypnotic-suggestion condition with study-specific suggestions and 4) post-hypnosis. The first and second studies included a common EEG experiment with nine highly hypnotizable participants. In the first study, EEG spectral power was measured and analyzed at ten frontal, central, and posterior/occipital electrodes. In the second study, the MMN was recorded at three frontal electrodes using a passive oddball paradigm with sinusoidal standard (500 Hz) and deviant (520 Hz) tone stimuli. Both studies included in the hypnotic-suggestion condition suggestions aimed at altering the tone perception (“all tones sound similar in pitch”). The third study examined, in adults with ADHD and in healthy control participants, whether hypnotic suggestions can influence performance in a three-minute version of the auditory CPT. The suggestions aimed at improving speed and accuracy. The fourth study used a controlled, randomized design in investigating the effectiveness of hyp¬notherapy in treating adults with ADHD. It compared the six-month follow-up outcome of the hypnotherapy with the outcome of a short CBT in various self-report symptom scales. Repeated-measures analysis of variance and t-tests were used in the statistical analysis of the studies. Results. The results of Study I revealed no EEG power changes between pre-hypnosis and hypnosis conditions, challenging the current understanding that the increase of theta power is a marker of the hypnosis state. Contrary to the results of a few earlier studies, no statistically significant differences in the MMN amplitudes between the conditions were found in Study II, indicating that the auditory pre-attentive processing may not be influenced by hypnosis or hypnotic suggestions. Study III indicated that hypnotic suggestions have an effect on the reaction times in the CPT both in ADHD adults and healthy control participants. Study IV revealed that the treatment benefits remained during the six-month follow-up with both hypnotherapy and CBT groups when measured with self-report ADHD symptom scales. The benefits of hypnotherapy and CBT, however, differed in general psychological well-being, anxiety and depression, and approached significance in the ADHD symptoms scale, indicating a better long-term outcome for hypnothera¬py. Conclusion. Results of the present thesis indicate that: 1) the spectral power of EEG in the theta band cannot be used as a reliable marker of the hypnotic state in highly hypnotizable participants; 2) hypnotic suggestions can be used to influence performance in a sustained attention reaction time task, but they do not modulate the early pre-attentive auditory information processing, reflected by MMN; 3) hypnosis, hypnotic suggestions, and short hypnotherapy treatments can be successfully applied to adults with ADHD to improve their performance in a sustained attention reaction time task, and to reduce their ADHD and other symptoms in a long-lasting (at least half a year) way. Thus, hypnosis/hypnotherapy seems to be a usable treatment method for the ADHD adult population.