What are depression and bipolar disorder? - Chapter 25

Which syndromes exist?

Depression

A depression manifests itself on both psychological and physical level. The depressive mood and / or anhedonia (not being able to experience pleasure) and / or loss of interest are the main characteristics that will cause the patient to neglect himself and the environment. The above-mentioned symptoms must be present for at least two weeks combined with at least four of the following: feelings of guilt, continuous thoughts of death, feelings of inferiority, anxiety, tiredness, loss of energy. Changes in appetite and body weight, sleeping problems, psychomotor agitation or inhibition, and a decreased libido may also occur. Frequently mentioned cognitive problems are related to the ability to think, focus attention, and making decisions. The physical symptoms have no physical cause.

Mania

A mania is the emotional opposite of depression. There is a continuous and abnormally elevated (euphoric), uncontrolled and excited (expansive), or irritable mood, and the mood change must be accompanied by persistently increased activity or energy levels. Symptoms such as inflated self-esteem, excessive optimism, or grandiosity may also occur. Speech is often accelerated and psychotic symptoms occur regularly. The libido increases as well as the energy. Sleep is suddenly no longer important. A distinction is made between a manic episode (at least a week or less than a week when hospitalization is necessary) and a hypomanic period (the manic symptoms are less severe).

The difference between unipolar depression and bipolar disorder

One in seven people develop a depressive or unipolar disorder, usually between the ages of 25 and 40 years. Women are twice as likely to develop depression as men. On average, depression lasts for eight months but four in ten patients experience a relapse after recovery. The bipolar (manic-depressive) I disorder (depression and mania) is just as common among men as it is among women; the bipolar II disorder (depression and hypomania) is more common in women. Both disorders usually starts in early adulthood and is lifelong.

The dimensional approach entail

In the DSM a clear distinction is made between depression and (hypo)mania, while the more and more scientists are arguing for a dimensional treatment, where both are on one continuum.

What does depression do to the body?

Depression is the result of a heterogeneous aetiology. Changes occur in the stress response system, monoamine system and immune system. Bipolar disorder also has such a heterogeneous aetiology.

Which cognitive impairments are there?

Earlier in this chapter, the majority of clinical issues have already been listed. The cognitive disturbances are partly secondary to this problem. The main disorders in depression are within the domain of psychomotor speed, sustained and selective attention, executive functioning and declarative memory. In the case of a depressive episode, the disorders in executive functioning and attention are in the foreground; in the case of chronic depression, memory problems are especially important. The symptoms of a manic syndrome are distractibility, increased risk-taking, and an increase in goal-oriented activities. The cognitive impairments that are part of a mania are experienced as more serious, more complex and more variable than the impairments in depression. The executive disorders are also more prominent in a mania. In the case of a depressive and bipolar disorder, there appears to be a global disruption of information processing. For example, in some patients, conscious and controlled information processing is impaired. The accompanying cognitive effort hypothesis states that the reduced performance on neuropsychological tasks can be explained by the lack of controlled information processing. However, the hypothesis does not explain the reduced performance on attention tasks. The second possible explanation for the reduced performance on cognitive tasks lies in the response at making a mistake: once depressed patients realize that they have made a mistake, they will make mistakes faster than healthy controls. A third explanation lies in a lack of motivation.

Cognitive impairment

As soon as the mood disorders disappear, most cognitive impairments also resolve. In this case, the severity of these state-related cognitive impairments is correlated with disease factors such as the number of episodes and the duration of the disease. However, sometimes these disorders persist even when the disease is not present (during symptom-free, euthymic periods), making them a 'trait' characteristic. The cognitive symptoms of bipolar patients in particular often persist when the disorder is not present (in particular the speed of information, executive control, fluency and working memory).

Demographic factors

Cognitive impairments are often more severe in elderly people with a depressive or bipolar disorder than in younger patients. The precise cause of cognitive impairment in mood disorders is still unclear, but it is certain that there is a complex interaction between environmental, genetic, developmental neurological and neurodegenerative factors.

What are cognitive side effects caused by treatment?

The side effects of medication

Lithium is a mood stabilizer, and is the first choice of medication in bipolar patients. Lithium can also be prescribed for patients with therapy-resistant unipolar depression. Some studies argue that lithium causes (severe) cognitive complaints. On the other hand, there are a lot of studies that report positive effects of lithium in the long term. This discrepancy is central to the current discussion about the neuroprotective versus the neurotoxic effects of lithium (Fountoulakis and colleagues, 2008). All possible side effects are reversible once the medication is stopped. Benzodiazepines have a negative effect on the speed of information processing, memory and attention. For depression, an SSRI (selective serotonin reuptake inhibitor) is the most prescribed drug and would not involve any negative cognitive risks.

The side effects of electroconvulsive therapy

In the case of a severe medication-resistant depression or mania, electroconvulsive therapy (ECT) can be chosen. ECT is the best method of treatment for depression, even better than SSRIs. However, due to the negative / somewhat frightening atmosphere about "electroshock therapy" and the possible cognitive side effects, there is a high threshold for application. The most common cognitive side effect is memory impairment: both anterograde and retrograde amnesia can occur. The anterograde amnesia is transient and disappears within a month; the retrograde amnesia (especially for recent events up to three months before treatment) remains longer.

Which cognitive biases are involved?

Mood biases

Because of a bias in information processing, there is a preference for processing negative (mood-congruent) information. Sometimes this bias is permanent. Teasdale's differential activation hypothesis (1988) states that patients with a history of depression can relapse more easily: a slight drop in mood can reactivate latent negative self-schemas because they have been linked to the depressed mood during an earlier episode of depression. A cognitive bias in unipolar depression can be found in various cognitive domains, in particular in attention and memory. Not much research has been done into a bias in bipolar patients, but it seems that there is indeed a positive equivalent of the attention bias just mentioned. In addition to a bias in information processing and attention, there is also a bias in explicit memory: mood-related information is processed more extensively, and this information is frequently associated with other information so that memories for such stimuli become stronger. A bias in implicit memory has not been demonstrated yet.

Which bias plays a role in social cognition?

The 'attributional style' is the extent to which people attribute events to an external cause or to themselves. This style is another form of bias. In depressive patients a negative attributional style is often found (the negative events are caused by themselves while the positive events have an external cause), and in manic patients a positive attributional style is found. Patients with bipolar disorder also have a disorder in ToM and the recognition of emotions in others. These disorders within social cognition remain present in euthymic episodes of bipolar patients.

What does neuroimaging show?

The processes involved in emotion regulation are dependent on and shaped by the ventral and dorsal areas of the brain. The ventral system includes eight areas of the brain: the amygdala, insula, VLPFC, OFPFC, the ventral ACG, the ventral striatum, the thalamus and brain stem. This system plays an important role in the interpretation of emotional meaning and the production of states of mind. The dorsal system comprises four regions: the DLPFC, DMPFC, the dorsal ACG and the hippocampus. This system is mainly involved in the regulation of mood. A bipolar state of mind may be due to a dysfunction in inducing and controlling a state of mind; A depressed state of mind seems mainly to be a dysfunction in the control of the emotional response.

What does structural imaging show?

In bipolar patients there are changes in temporal lobe volume, reduced prefrontal volume and, on the contrary, the amygdala is larger (Keener & Phillips, 2007). These areas may be the top-down cause for the changes in emotion regulation as described above. Furthermore, there is also less volume in the DLPFC and ventral PFC that both. Especially the latter is related to modulating mood, based on integrated cognitive and emotional information. In both a depressed patient and a bipolar patient, there are more white matter hyperintensities. These are most common in bipolar I disorder followed by bipolar II disorder and eventually unipolar depression. The volume of the hippocampus is also smaller in a depressed patient. There is also atrophy in the OFC, ACC, the putamen, nucleus caudatus, and the amygdala. This data has no diagnostic value and does not necessarily have to be present.

What does functional imaging show?

Multiple parts of the PFC show a reduced activity (hypofrontality) in bipolar patients, which causes disturbances in executive functions, also in euthymic periods (trait). The hypofrontality of the DLPFC is found in the depressive and manic periods; the hypofrontality of the medial frontal cortex and the ACC are overactive during mania but underactive during depression. There is also a continuous increase in limbic activity. This dysfunctional circuit between the prefrontal and subcortical areas is probably the cause of bipolar disorder. In patients with depression there is an increased metabolism in the ventral limbic areas, amygdala and thalamus. This higher metabolism is positively related to the severity of the depression. The overactivity in the areas associated with the memory is probably responsible for the memory bias.