How is depression clinically defined?
In clinical terms, depression is defined by the presence of a cluster of symptoms. The Diagnostic Manual used by many psychologists and psychiatrists cites nine symptoms of depression, of which five must be present for a two-week period.
The symptoms are both psychological and physiological, but key psychological symptoms, including depressed mood and loss of interest, must be present for a diagnosis to be given.
What are the main symptoms of depression?
The main psychological symptoms of depression are depressed mood and negative views of the self, including feelings of guilt and worthlessness. In severe cases, people may experience feelings of helplessness, hopelessness and suicidal thoughts.
Physiological symptoms can include changes in sleep patterns (difficulty sleeping, sleeping too much), eating patterns (appetite loss / increase) and tiredness. People also can experience changes in activity levels, such as either feeling lethargic and conversely quite agitated.
What was previously thought to cause people with depression to feel their lives were out of control?
A combination of factors has been thought to cause people with depression to feel ‘out of control’. So for example, early research carried out in the 1960s and 70s showed that when people have experiences of negative events that they can’t control the occurrence of, they tend to show the symptoms of depression.
However, they also then do not tend to recognise when they can control events. In other words, this feeling of helplessness stems from earlier learning experiences (learned helplessness).
In addition, psychologists, such as Beck, proposed that people with depression think negatively, about themselves, their world and the future. This negative thinking pattern causes people with depression to evaluate situations in a negative manner, such as ‘I can’t control this’.
Another rather controversial view, was that rather than being negatively biased, depressed people are actually realistic in their assessment of how much control they have over things.
The implication of this depressive realism view, is that when people with depression express their feelings that they can’t control their world – they are right, they can’t. Moreover, healthy people view the world through rose coloured glasses.
How did your research into depression and changes in the way depressed people perceive time and process their surroundings originate?
Our research on depression and changes in time perception originated from our early attempts to study the depressive realism effect. Along with Robin Murphy of the University of Oxford, we found that time was an important variable in these experiments.
Differences between depressed and non-depressed people’s judgements of how much control they had in any given situation only emerged when experimental tasks were presented over a longer periods of time.
This led us to explore amongst other things literature on time perception and depression. Sure enough, we found that people had being studying slowed perception of time in depression since the early 20th century, though methods used and findings had been inconsistent and unreliable. In spite of this there was a strong suggestion that time perception was slowed in depression.
In addition, we wondered what kind of impact slowed time perception might have on people’s feelings of control. One aspect to this is simple, actions and subsequent outcomes might seem to be further apart in time.
Since the work of the philosopher Hume, closeness in time has been considered to be critical for two events to be considered to be causally related or controlling each other. So if actions and outcomes seem further apart in time, then people may think they have less control.
However, another less obvious aspect to this is the impact of slowed time perception on the perception or processing of environmental information and what that has to do with control!
Well, you might think of assessing your own control over events in the following manner. If I don’t have control over things, which happen around me, what does? After asking that question, I might look around to my environment (whatever that is) and compare my own control to the control that the environment seems to exert over these events.
Take a simple scenario. I press the light switch in my office. Sometimes the light switches on, sometimes it doesn’t. Sometimes, when I am sitting at my desk, the light flickers on and off. Am I in control of this light? No, it is something about the wiring or the status of the electrical installation, which causes these light flashes, rather than my actions. In other words, I have no control and the environment has more than me!
If a person has slowed time perception, then logically they have more psychological time available to process environmental information, and thus process a stronger relationship between environment and outcome, as opposed to own actions and outcome.
Therefore our early research suggested that time and environmental processing were inter-related, and changes in this type of processing might be responsible for findings of depressive realism rather than any tendencies towards realism per se.
What did your research involve?
We presented people with computer tasks in which they were asked to assess how much control they had over the switching on of a brief music clip. People had lots of opportunities to press a button on a remote control and try to switch on the music, after which they rated their control over the music switching on.
We also measured levels of depression, anxiety and other variables, such as measures of education, attention, age and so forth.
In a series of experiments involving different amounts of control, we varied times between button presses and music switching on, and also the times in between those experiences – the times when people just experience their environment and wait for the next thing to happen, an analogue of every day life.
Over a series of experiments, we found that people who showed mild symptoms of depression were more sensitive to these time manipulations than people who were not depressed.
Why did you explore how healthy volunteers responded to simple tasks with varying levels of control as well depressed volunteers?
Exploring data from healthy volunteers as well as mildly depressed volunteers is a very important aspect to a scientifically sound study.
Firstly, the specific manipulations we used in this series of studies had not been tested simultaneously in previous research. It was important to see how people typically respond to these manipulations.
Secondly, testing both groups is time consuming but it provides us with baseline data against which to compare data derived from mildly depressed people.
Furthermore it is very important to understand how healthy people process information. Understanding healthy states is as important as understanding depressive states.
What did your research find to be the difference between these two groups?
The key difference between the two groups was in how they responded to time manipulations. Volunteers who were mildly depressed, produced ratings of their control over outcomes that were influenced significantly by time.
Effects on the non-depressed were weaker and less consistent. However the nature of the effects depended on the amount of control available to participants. For example, when there was a strong degree of control available over the music switching on, longer time periods weakened the perception of control.
However, when depressed participants actions prevented the music from switching on, then depressed participants perceived more preventative control.
What else did your research find?
Exploring different levels of control was important and provided clues to underlying mechanisms. As we describe above, slowed time can impact on control (and probably other thinking tasks) in different ways.
When depressed participants could control the music switching on, longer periods of time reduced the extent to which they thought they could control the music. However, when their actions prevented the music from switching on, then longer periods of time enhanced judgements of prevention.
Taken together, these findings pointed towards time effects as influencing how people process the environment. If the person has control, yet the environment is perceived to also have strong control, then people will think they have little control and are helpless.
However, when people’s actions prevent outcomes from occurring, this time perception bias will enhance the sense of prevention. This is particularly important because it tells us that it is not just internal psychological processes which are important here, it is also the opportunities which people have access to that will affect their experiences of control.
What do you think are the reasons why depressed people experience time as passing more slowly?
This is a very interesting question and one that we are currently investigating!
One suggestion relates to the psychological processes that allow us to perceive time passing and how long it has lasted for. The general idea is that there are biological mechanisms which function similarly to the ticking of a clock; our perception of time passing is based on the accumulation of ‘ticks’. Lots of ticks mean lots of time passed and vice versa.
Changes in the speed of the internal clock, or lapses in attention paid to time processes could all have the result of slowing down a person’s psychological perception of time. Such effects could be due to depression related changes in brain chemistry (e.g., levels of serotonin in the central nervous system) though this is not clear.
Furthermore, when people are depressed, they tend to ruminate meaning that they tend to engage in a lot of repetitive thinking about their feelings and what they might mean. These types of thought processes may well interfere with people’s ability to process time information.
One or all of these possibilities are reasons why depressed people might experience time as passing more slowly than others.
Were the results of your research surprising?
These findings add to a body of research that we, and others, have carried out of over the last number of years. We have painstakingly shown that very subtle changes in quite basic psychological processes, like processing time and the environment, can lead to important changes at a higher level – how much control we think we have over our world.
This means that in addition to using therapies which address say negative thoughts we also need interventions which seek to recalibrate some of the more basic psychological processes.
Do these findings shed any light on how people with depression can be treated?
In terms of treatment, for some people antidepressant treatment is necessary and successful. Psychological interventions can also be used along with antidepressants or alone. However, treatments, which seem to be very relevant to our findings, involve an aspect of mindfulness training.
Mindfulness or being mindful is about focussing attention on the here and now, the present moment, in a non-judgemental manner. This can be contrasted to constantly thinking about worries or plans, being preoccupied, and in sense behaving automatically with little appreciation of the here and now.
Therapies involving mindfulness have been shown to be successful in the treatment of depression and importantly in preventing recurrence and relapse. Our findings may well speak to underlying reasons why this type of treatment is successful.
Can anything be learnt about depression and time perception by studying the way in which children perceive time?
It is certainly possible that research on the way children perceive time could be informative in terms of understanding depression. This is because the ability to perceive time develops through childhood, and is also affected by emotional states. For example, time flies when you’re having fun!
Studying developmental changes in this type of processing, possibly in groups with a high risk for depression, has the potential to inform us about any longitudinal differences in time processing which are relevant to depression.
Where can readers find more information?
Readers can email me on: [email protected] or contact me via twitter on @MsetfiLab
I tend also to post information and links to academic papers to my website (under resources) as this becomes available:
I also post tools for research use, which anyone is welcome to download and use.
Our latest research paper can be found in PLOS ONE: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0064063
About Dr Rachel Msetfi
Dr Rachel Msetfi is a Senior Lecturer in Psychology at the University of Limerick in Ireland where she is the Course Director of the undergraduate psychology programme.
Rachel received her PhD from the University of Hertfordshire in the UK. She also lectured in Statistics and Psychopathology at Hertfordshire, before taking up a post as a Lecturer in Research Methods at the University of Lancaster in the UK teaching on the clinical psychology programme there.
Rachel then moved to Ireland to take up her current post where she is also a member of the Centre for Social Issues Research.
She is a chartered member of the British Psychological Society, a member of the Experimental Psychology Society, and has published papers on depression, perceived control, time perception, context / environment processing amongst other topics in refereed journals.
The research described here was supported by the Economic and Social Research Council in a grant to Dr Rachel Msetfi (PI) and Dr Robin Murphy (CI) [grant number RES-062-23-2525].