Wednesday, 22 April 2015

Why Are Some People Treatment Resistant to Antidepressants?

Every year well over 200 million prescriptions are handed out for antidepressants in the United States. Of the people who take antidepressant medications some will feel a certain level of relief and some won’t benefit at all. So, if depression is simply due to an imbalance in neurotransmitters, why are some people ‘treatment resistant’ when they take the very medication designed to correct the problem?

Professor Eva Redi, of the Northwestern University Feinberg School of Medicine, believes the answer lies in the faulty assumptions people have been making about the nature of both stress and depression. During the 2009 Neuroscience conference in Chicago, she told delegates there are two central problems. The first is the assumption that stress from major life events can cause depression and the second is that depression is due to an imbalance of neurotransmitters such as serotonin and dopamine.

Redi studied rats with behavioral and physiological abnormalities found in humans with major depression. First, she isolated the specific genes related to depression in the hippocampus and amygdale regions of the brain. Rats were then exposed to two weeks of chronic stress, so enabling her to identify the genes that responded to stress as well as those that responded to depression. After examining 30,000 genes, 254 were related to stress, 1,275 to depression and just five were found in both samples.

From this, Redi concludes that stress does not cause the same molecular changes as depression. The results also suggest that neurotransmitter imbalance may not be the trigger for depression. The real cause of depression, Redi suggests, appears to start in the development and function of neurons. Antidepressant medications act like a band-aid in that they do not target the cause of depression, only the effect. “If depression was related to neurotransmitter activity, we would have seen that,” she said.


Sceptics may argue that the function of the rat brain is vastly different to that of a human brain. To this Redi states, “the similarities between these regions of the human and rodent brain are remarkable. The hippocampus and amygdala are part of the so-called ancient lizard brain that controls survival and are the same in even primitive organisms.”

Wednesday, 1 April 2015

Is Stress a Killer?

Personal catastrophes occur on a daily basis but does stress actually do us any real harm? Sufficient evidence is now available to point to stress having an effect on health, but there has always been a lingering uncertainty as to whether stress can lead to an early grave.

Anna Phillips and Douglas Carroll, two health psychologists from the University of Birmingham, U.K., have taken stock of the evidence that links both stress to illness and stress to mortality. Their review is published in the February edition of The Psychologist. The authors point to a situation of good links between stress and illness but conflicting evidence in the association between stress and mortality. The reason, they say, is because not only is stress measured in different ways, it is not always the case that stress is bad for us. This presents a puzzle that researchers have yet to solve.

Two approaches to the measurement of stress predominate. The first relies on self reports from individuals’ as to how they feel stress affects them. The second focuses on exposure to stressful life events. Self report measures are easy and popular, but as the authors point out, they have their weaknesses. For example, older people are not as used to thinking of themselves as feeling stressed and in some blue-collar environments the term ‘stress’ is something that may not even be in the person’s vocabulary. Measures of life events is less prone to bias but a simple count of events deemed as stressful is also problematic due to differences in personal perceptions of stress.

What complicates the picture further is the fact that the effect of stress on the body can bring about benefits as well as problems. In the way a dose of influenza enhances antibody response and boosts the immune system, so exposure to limited levels of stress appears to have similar protective effects. However, as Phillips and Carroll also indicate, certain catastrophes can and do precipitate illness and death. Increased admissions to heart units have been recorded in various countries following earthquakes. Yet in England, emergency admissions for heart attacks increased 25 percent following defeat in the 1998 World Cup soccer match!

What are we to make of information such as this? The authors feel it is right to remain cautious about any possible links between stress and death. New models of stress are being developed in line with greater understanding of the delicate and intricate balance between psychological stress and its effects on the body. Until we know more, the jury is out.

Source:

Phillips, A., Carroll, D (2009) Heading For an Early Grave? The Psychologist. 22. 2. 122-125.