Cardiovascular Stress Testing in the Laboratory

Good general reference Kamarck & Lovallo (2003) Psychosomatic Medicine, 65, 9-21 Discusses; CV reactivity stability over time CV reactivity over different tasks Types of tasks that are useful Laboratory – Real life

Ideally we would measure cardiovascular reactions to stress in real life….. However, this approach come with a number of problems

1.How do we know when people will experience stress? 2.What if we choose people under a lot of stress (e.g. caregivers)? 3.Will chronically stressed people be stressed all the time? 4.Why not recruit people who were stressed in the past?

5.Most importantly, CV measures still quite difficult to use in the field Portable or ambulatory BP and HR monitors Often bulky Visible to others For BP usually record periodically not continuously

Best option for real world events; Events that are stressful but not too upsetting Events that occur at predictable times E.g. exams, driving tests, etc Standardised / timed

However, still problems; Limited in measures we can use e.g. blood pressure cuff Critical not to distract people Still lots of confounds – e.g. smoking, caffeine

So what are your options? Aim -> Look at CV reactivity during stress Use an artificial laboratory stress task

Advantages; Complete experimental control Standardisation Task mixing (if interested in effects of stress on X) Can make sure CV measures working OK

What kind of tasks? Ethical considerations Demanding not traumatic

Ten most common lab stressors (in no order)

Reaction Time tasks Respond to tone as fast as possible Simple or choice versions

Public Speaking Short period to prepare a speech Typically fake job talk, defendant in court, etc Audience / video camera

Mirror Tracing Trace a complex shape Using only mirror image Usually distance / number correct in time allowed

Mental Arithmetic Either backwards counting with large numbers Or mentally solving rapidly presented maths problems

Stroop Task Colour – word task Name ink colours Speeded test RED BLUE YELLOW GREEN

Cold Pressor Task Hand /foot in iced water 1-2 mins (as long as possible) Often painful

Distress Recall Relive stressful event Usually frustrating past events Describing all the details

Video games Tracking a target Responding quickly Parts requiring good hand-eye co- ordination

Ravens Matrices Visual logic puzzles Must choose next in series Often timed

Distressing Films Passively watching nasty films Car crashes, autopsy, childbirth, industrial accidents, horror films, etc

One of the best lab tasks Combines public speaking and mental arithmatic; The Trier Social Stress Test Kirschbaum, Pirke, & Hellhammer (1993)

Trier Social Stress Test Part 1 Prepare Imagine youve applied for a job as a psychologist. In 5-10 minutes you will give a speech to the selection committee about why you would be good for this job. You must speak for 5 minutes without notes and you will be audio and video-taped so we can analyse your body language.

Trier Social Stress Test Part 2 Speech The committee – 2-3 people Microphone and video camera (switched on in silence). Begin speech Silence for >20 secs = you still have time, please continue Further silence = questions

Trier Social Stress Test Part 3 Counting Thank you – we will now move onto a second task Count backwards (out loud) from 1687 in 13s Quickly & accurately as possible Mistake= start again Committee still present Camera / microphone still on

Control task depends on your measure (BP, HR, cortisol, etc) Cortisol – quiet period at the start (before they know the nature of the task) BP/HR – quiet task at end (after a break) with similar demands but no stress

Debrief Participants told no recordings made Told task designed to elicit stress response and committee instructed to appear formal / unfriendly

Data from the lab (n=24) IndividualsAverage

Data from the lab (n=24) IndividualsAverage

Data from the lab (n=1) High Speech ReactorHigh Maths Reactor

Data from the lab (n=1) Non-Reactor

The Trier task has been shown to elicit significant stress responses in Both males and females Both children and adults Both younger and older adults Kudielka, Buske-Kirschbaum, Hellhammer, & Kirschbaum. (2004) Psychoneuroendocrinology, 29, NB – This paper is quite complicated – the main point to note is that they showed the Triers effectiveness in both genders, and all age groups.

Trier task = most effective laboratory task for inducing stress reactions (measured with cortisol) Dickerson, S.S. & Kemeny, M.E. (2004) Psychological Bulletin, 130, – READ ONLY ABSTRACT & DISCUSSION

Dickerson & Kemeny (2004) conclude Trier type tasks = effective because they include; 1.Social-evaluative threat (when other people may make negative judgements about the participant, or when poor performance would reveal a lack of ability) 2.Uncontrollability (when participants best efforts are not sufficient to prevent negative outcome)

To understand these last 2 references – need to know what the HPA axis is HPA axis = Hypothalamic Pituitary-Adrenal Axis Major part of the neuroendocrine system which controls the release of stress hormones

Under Stress, the HPA axis; Hypothalamus produces corticotrophin releasing hormone (CRH) CRH causes the Pituitary gland to release adrenocorticotrophin (ACTH) ACTH causes the Adrenal glands to release epinephrine (adrenaline), norepinephrine (noradrenaline) and cortisol (amongst other things) These stress hormones help the body respond to threat by increasing HR and BP, diverting blood to muscles, speeding reaction time, releasing sugar to use as fuel, etc.

Worth remembering; Lab tasks arent perfect; Artificial Therefore lab reactivity may not relate directly to reactivity in real life (DJ to discuss)

In Summary Measuring stress during real life events = sacrificing experimental control Measuring stress in the laboratory = sacrificing ecological validity

Best strategy Combine both lab and field measures Use lab tasks with ecologically valid characteristics like the Trier

Any Questions Dr Julia Hay Room B38, William Guild