Stress v Anxiety in Autism - what's the difference.

First a lighthearted take

Stress is when you're stuck in traffic and late for an important meeting, while anxiety is when you're stuck in traffic and your brain starts to imagine all the worst-case scenarios that could happen at the meeting. They both make you feel like you're about to lose your mind, but with anxiety, you have to deal with the added bonus of your own overactive imagination!

Stress and anxiety are like two sides of the same coin. They both make you feel like you're about to lose your mind, but with stress, you know exactly what's causing it, while with anxiety, you could be stressed out about being anxious, which just makes you more anxious. It's like a never-ending cycle of stress and anxiety, and the only way to break it is to find some humor in the situation and laugh it off!

Knock knock. Who's there? Stress. Stress who? Stress no more, it's the weekend!

Knock knock. Who's there? Anxiety. Anxiety who? Anxiety friend, can you please distract me from my own thoughts?

Stress: Hey Anxiety, why are you always so jittery? Don't you know how to relax?
Anxiety: I can't help it! You're the one who always makes me feel like the world is about to end.

I hope these made you smile before we get to the neuroscience. 

Physiological/Neurological viewpoint 

Stress and anxiety share some common mechanisms, but they also have distinct characteristics. Stress and anxiety also involve overlapping but distinct neural circuits. 

Stress is a physiological response to a real or perceived threat that involves the activation of the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS). This response is primarily regulated by the HPA axis, which involves the hypothalamus, pituitary gland, and adrenal glands. The HPA axis response to stress is mediated by the release of corticotropin-releasing hormone (CRH) from the hypothalamus, which activates the pituitary gland to release adrenocorticotropic hormone (ACTH), leading to the release of cortisol, adrenaline, and noradrenaline from the adrenal glands. These hormones increase heart rate, blood pressure, and glucose levels, and mobilize energy reserves to prepare the body for a "fight or flight" response.

The prefrontal cortex (PFC) is a higher brain region that modulates the HPA axis response to stress. The PFC is involved in regulating emotional responses and inhibiting inappropriate or maladaptive responses. Dysregulation of the PFC can lead to altered stress responses and increased vulnerability to stress-related disorders such as anxiety and depression. Additionally, chronic stress can lead to dysregulation of the HPA axis and associated physiological responses, which can have negative effects on physical and mental health.

Anxiety on the other hand is a complex emotional state that can occur in response to stress or other triggers, and it involves the activation of neural circuits that regulate emotional processing and cognitive control. The amygdala (fear and emotional processing) plays a key role in processing and responding to emotional information, while the prefrontal cortex (PFC) is involved in regulating emotional responses and inhibiting inappropriate or maladaptive responses.

Anxiety can be associated with increased activity in the amygdala, as well as changes in neurotransmitter systems, such as reduced GABA and increased glutamate levels. Anxiety disorders are associated with altered activity in neural circuits involved in emotional processing and regulation, including the amygdala, PFC, and anterior cingulate cortex (ACC). Studies suggest that autistics may have differences in the structure and function of these brain regions, which may contribute to altered emotional processing and regulation. For instance, some studies have shown that autistics may have increased amygdala volume and increased activation in this region in response to emotional stimuli, which may contribute to anxiety

Stress and anxiety may lead to similar changes in the HPA axis and SNS in autistics and NTs. However, there may be group differences in the cortisol response with some studies suggesting that autistics may have a blunted cortisol response to stress, which may be related to differences in the regulation of the HPA axis.

Behavioral Viewpoint

Stress and anxiety can have similar and overlapping symptoms, such as increased heart rate, sweating, and irritability. 

However, stress responses are typically short-lived and resolve once the threat has passed, while anxiety can persist for longer periods of time and can interfere with daily functioning. Anxiety can manifest as excessive worry or fear in response to a perceived threat or trigger, and can lead to avoidance behaviors or other maladaptive coping strategies.

Anxiety disorders are characterized by excessive worry, fear, or avoidance behaviors in response to perceived threats or stressors. In autistics, these behaviors may manifest differently or be more difficult to recognize due to social and communication differences. For example, autistics may engage in repetitive behaviors or have difficulty with transitions or changes in routine as a way of coping with anxiety. Additionally, social anxiety may be particularly relevant in autism, as social interactions can be particularly challenging and anxiety-provoking.

Needless to say, much more investigation is needed when it comes to anything autism and get us closer to translatable solutions. I hope I get to see solutions in my lifetime. 

Citations: 

1. Bitsika, V., Sharpley, C. F., Andronicos, N. M., & Agnew, L. L. (2016). Cortisol response to a social stressor in adults with autism spectrum disorder: Results from an experimental paradigm. Research in Autism Spectrum Disorders, 26, 11-20.

autistics had lower cortisol levels compared to neurotypicals in response to a social stressor. 

2.Corbett, B. A., Mendoza, S., Abdullah, M., Wegelin, J. A., & Levine, S. (2006). Cortisol circadian rhythms and response to stress in children with autism. Psychoneuroendocrinology, 31(1), 59-68.

autistic kids had a blunted cortisol response to a psychosocial stressor compared to neurotypicals

Dapretto, M., Davies, M. S., Pfeifer, J. H., Scott, A. A., Sigman, M., Bookheimer, S. Y., & Iacoboni, M. (2006). Understanding emotions in others: mirror neuron dysfunction in children with autism spectrum disorders. Nature Neuroscience, 9(1), 28-30. 

increased amygdala activation in response to fearful facial expressions in autistics compared to neurotypicals.

 Kerns, C. M., Newschaffer, C. J., & Berkowitz, S. J. (2015). Traumatic Childhood Events and Autism Spectrum Disorder. Journal of Autism and Developmental Disorders, 45(11), 3475–3486. doi: 10.1007/s10803-015-2491-4

Kleinhans, N. M., Johnson, L. C., Richards, T., Mahurin, R., Greenson, J., Dawson, G., & Aylward, E. (2008). Reduced neural habituation in the amygdala and social impairments in autism spectrum disorders. American Journal of Psychiatry, 165(8), 979-986.

increased amygdala activation in response to social and non-social stimuli in autistics compared to neurotypicals

Mazefsky, C. A., & White, S. W. (2014). Emotion regulation: concepts & practice in autism spectrum disorder. Child and Adolescent Psychiatric Clinics of North America, 23(1), 15–vi. doi: 10.1016/j.chc.2013.07.002

Noriuchi, M., Kikuchi, Y., Senoo, A., & Tojo, Y. (2010). The functional neuroanatomy of maternal love: mother's response to infant's attachment behaviors. Biological Psychiatry, 63(4), 415-423.

increased amygdala activation in response to emotional facial expressions in autistic children

Schumann, C. M., Barnes, C. C., Lord, C., & Courchesne, E. (2004). Amygdala enlargement in toddlers with autism related to severity of social and communication impairments. Biological Psychiatry, 55(12), 136-143.

autistics had increased amygdala volume compared to neurotypical children.

Tordjman, S., Anderson, G. M., McBride, P. A., Hertzig, M. E., Snow, M. E., Hall, L. M., ... & Ferrari, P. (2014). Plasma β-endorphin, adrenocorticotropin hormone, and cortisol in autism spectrum disorders with regression. Biological psychiatry, 76(4), 275-281.

autistics had lower basal cortisol levels compared to neurotypicals 

van Steensel, F. J. A., Bögels, S. M., & Perrin, S. (2011). Anxiety Disorders in Children and Adolescents with Autistic Spectrum Disorders: A Meta-Analysis. Clinical Child and Family Psychology Review, 14(3), 302–317. doi: 10.1007/s10567-011-0097-0

Wigham, S., McConachie, H., Tandos, J., & Le Couteur, A. S. (2012). The characteristics of anxiety in autism spectrum disorder: A population-based twin study. Journal of Autism and Developmental Disorders, 42(9), 1818–1824. doi: 10.1007/s10803-011-1425-6