Health scan: Autism and the smell of fear

The team investigated smells that announce such emotions as happiness, fear or aggression to others.

A child with autism plays with other children (file) (photo credit: REUTERS)
A child with autism plays with other children (file)
(photo credit: REUTERS)
The sense of smell may play a central role in autism, according to research at the Weizmann Institute of Science that was reported recently in Nature Neuroscience. Autism typically involves the inability to read social cues, especially visual difficulty in interpreting facial expression.
Prof. Noam Sobel and his lab team in the Rehovot institute’s neurobiology department show that people on the autism spectrum have different – and even opposite – reactions to odors produced by the human body. These odors are ones that we are unaware of smelling, but which are, nonetheless, a part of the nonverbal communication that takes place between people and that have been shown to affect our moods and behavior. Their findings thus may provide a unique window on autism, including, possibly, on the underlying developmental malfunctions in the disorder, they suggest.
The team investigated smells that announce such emotions as happiness, fear or aggression to others. Although this sense is not humans’ primary sense, as it is in many other mammals, we still subliminally read and react to certain odors, they explained. For example “smelling fear,” even if we cannot consciously detect its odor, is something we may do without thinking. Since this is a form of social communication, Sobel wondered whether it might be disrupted in a social disorder like autism. To conduct their experiments, Sobel and lab members Yaara Endevelt-Shapira and Ofer Perl, together with other members of his lab, devised a series of experiments with a group of participants on the high functioning end of the autism spectrum who volunteered for the study. To begin with, the researchers tested the ability of both autistic and control volunteers to identify smells that can be consciously detected, including human smells like sweat.
Two groups were then exposed to either to the “smell of fear” or to a control odor. The smell of fear was sweat collected from people taking skydiving classes, and the control odor was sweat from the same people, only this time it had been collected when they were just exercising – without feeling fear.
Although neither group reported detecting dissimilarities between the two smells, their bodies reacted to each in a different way. In the control group, smelling the fear-induced sweat produced measurable increases in the fear response, for example in skin conductivity, while the everyday sweat did not. In the autistic men, fear-induced sweat lowered their fear responses, while the odor of “calm sweat” did the opposite: It raised their measurable anxiety levels.
Next, the group created talking robotic mannequins that emitted different odors through their nostrils. These mannequins gave the volunteers, who were unaware of the olfactory aspect of the experiment, different tasks to conduct. Using mannequins enabled the researchers to have complete control over the social cues – odorbased or others – that the subjects received. The tasks were designed to evaluate the level of trust that the volunteers placed in the mannequins – and here, too, the behavior of autistic volunteers was the opposite of the control group: they displayed more trust in the mannequin that emitted the fear-induced odor and less in the one that smelled “calmer.”
In continuing experiments, the researchers asked whether other subliminal “social odors” have a different impact in autism than in control groups. In one, the volunteers were exposed to sudden loud noises during their sessions while at the same time they were also exposed to a potentially calming component of body odor named hexadecanal. Another automatic fear response – blinking – was recorded using electrodes above the muscles of the eye. Indeed, the blink response in the control group was weaker when they were exposed to hexadecanal, while for those in the autistic group this response was stronger with hexadecanal.
Thus the autistic volunteers in the experiment did not display an inability to read the olfactory social cues in smell, but rather they misread them. Sobel and his group think that this unconscious difference may point to a deeper connection between our sense of smell and early development. Research in recent years has turned up smell receptors like those in our nasal passages in all sorts of other places in our bodies – from our brains to our uteri. It has been suggested that these play a role in development, among other things. In other words, it is possible that the sensing of subtle chemical signals may go awry at crucial stages in the brain’s development in autism.
Cigars have a popular reputation for being safer than cigarettes, but they may be just as harmful and addictive (Prime Minister Benjamin Netanyahu take note!).
Researchers at Penn State University note that small cigars have just as much if not more nicotine than cigarettes.
The researchers analyzed the nicotine in smoke from popular brands of “small” or “filtered” cigars (cigars that are almost identical to cigarettes except they’re wrapped in leaf tobacco instead of paper). The researchers found that the level of nicotine found in small cigar smoke is similar to or greater than cigarette smoke.
“There seems to be a perception in the public that cigars are not as harmful as cigarettes,” said Reema Goel, research associate in the Penn State College of Medicine. “But our study shows that nicotine is pretty high in this class of cigars, and future regulation that affects cigarettes should also affect these cigars.”
Prof. John Richie, a public health sciences and expert at Penn State, said the confusion surrounding the safety of cigars may stem from tobacco companies using clever tricks to get around current regulations.
“There are many misconceptions about cigars. The truth is, cigar smoke is inhaled and is just as harmful to the lungs,” Richie said. “Tobacco companies use loopholes in the way these products are taxed to allow these small cigars to be substantially cheaper than cigarettes. They can also get around the regulation that says cigarettes can’t be flavored, to avoid making them appealing to children. These small cigars come in all kinds of flavors.”
“Nicotine is the reason why people smoke cigars, just as it is the reason they smoke cigarettes,” he continued. “Many of the regulatory strategies that are currently being studied are ways to reduce nicotine exposure from tobacco products, to make them non-addicting. We’re seeing from the results that these should also apply to small cigars.”
The researchers – who published their findings in the journal Nicotine and Tobacco Research – compared nicotine delivery in eight common brands of small cigars with two types of cigarettes commonly used in research.
A machine took two-second puffs every 60 seconds, with no filter vents blocked. It also took two-second puffs, but they were only 30 seconds apart, and the vents were blocked with tape. Nicotine was then extracted and analyzed from both groups.
The researchers found that the mean average nicotine delivered by the small cigars sampled was 1.24 milligrams per cigar, compared to 0.87 in cigarettes. Using the second method, the mean average of nicotine delivered by the small cigars was 3.49 milligrams per cigar, compared to 2.13 in cigarettes.
“To me, the amount of nicotine in some of these brands was surprising,” Goel said. “One brand in particular, a clove-flavored option, had the highest nicotine delivery and is also a very popular brand. It’s interesting that it’s clove-flavored, because such high levels of nicotine causes nausea, and perhaps that clove flavor is there to ease that nausea.”
“These products are basically cigarettes. They’re as harmful to you as cigarettes, if not more so,” Richie said. “It’s very important for the consumer to understand that these are not products that are less harmful, and for regulations to include these small cigars in with cigarettes.”