Common types of antidepressants
Medication in the form of pills
SSRIs are the most widely prescribed antidepressant drug in the current treatment for depression (Harmer, 2008). The drug includes fluvoxamine, fluoxetine, citaloprma, escitalopram, sertraline and paroxetine and is effective for treating symptoms of depression and anxiety (Gunnell et al., 2005). SSRIs are serotonin specific and only influence serotonin and not other neurotransmitters such as norepinephrine and dopamine (Gunnell et al., 2005). SSRIs also have less negative side effects compared to other types of antidepressants.
SNRIs are made up of duloxetine, venlafaxine and desvenlafaxine and is less popular then SSRIs. They prevent the reuptake of serotonin and norepinephrine by inhibiting the serotonin transporter (SERT) and the norepinephrine transporter (NET) (Dell'Osso et al., 2010). This drug may be more beneficial in treating a wider range of symptoms associated with depression due to this dual action (Dell'Oosso et al., 2010).
TCAs are made up of amitriptyline, nortiptyline, clomipramine, dothiepin, doxepin, imipramine and trimipramine. This antidepressant has more severe side effects than SSRIs but is used to treat treatment-resistant depressions (Anderson, 1998). TCAs block serotonin and norepinephrine re-uptake and also prevent action of acetylcholine.
MAOIs inhibit the action of monoamine oxidase which is a type of enzyme found in the brain that breaks down neurotransmitters such as serotonin (Volz & Gleiter, 1998). Like SSRIs, it increases serotonin levels and is used only if SSRIs were unsuccessful (Volz & Gleiter, 1998). The active components in this drug includes phenelzine and tranylcypromine.
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How do antidepressants affect emotion?
Tryptophan and low serotonin levels
Serotonin levels in the brain relies on the activity and availability of its precursor amino acid (tryptophan) (Harmer, 2008). The relationship between low serotonin levels and emotional processes have been studied with the administration of amino acid mixtures which decrease the availability of tryptophan in the brain (Reilly et al., 1997). Low tryptophan levels have been found to lower mood in recovered depressed patients (Ruhe et al., 2007), and has been linked to a reduction in the processing of positive versus negative affective emotional information (Harmer, 2008). A study by Murphy et al. (2002) tested this and found that a reduction in tryptophan levels slowed responses to positive verbal stimuli in an affective go-no go task. In addition, patients with lower availability of tryptophan also experienced a reduction in memory for positive affective information (Klaasen et al., 2002) and had increased interference for negative stimuli in a Stroop experiment by Evers et al. (2006). These reductions of positive biases have been linked to increased neural activity in the ventromedial prefrontal and sub-cortical areas (Roiser et al., 2007) (7) which is similar to the neural activity found in clinically depressed patients (Elliott et al., 2002). In light of these findings, it has been suggested that low serotonin levels due to decreased availability of tryptophan, factors associated with depression, is related to disturbances in the processing of emotional material (Harmer, 2008).
Repeated SSRI treatment
A study conduced
by Harmer et al. (2004) found that after 7 days of continued SSRI administration patients were more inclined to see ambiguous facial expressions as happy. He also found that patients were able to memorise positive personality adjectives more accurately. Other studies have supported these findings and found reductions in threat-relevant processing after continued SSRI administration (Harmer et al., 2004). In particular, perceptions of disgusted, angry and fearful facial expressions were seen to reduce along with an increase in mood. Function resonance imaging studies have also found neural activity consistent with emotional changes during treatment. Reductions in amygdala, medial prefrontal, and fusiform responses to facial expressions eliciting fear and increases in fusiform responses to happy facial expressions were observed (Norbury et al., 2007). SSRI treatment also improved coupling between the amygdala, prefrontal cortex, striatum, and thalamus which are important neural networks associated with depression (Chen et al., 2007). fMRI data suggests that SSRI affects autonomic evaluation of emotional stimuli and also attentional processing (Harmer, 2008). Antidepressants appears then to have the ability to reduce emotional processing for negative stimuli and increase emotional processing for positive stimuli (Harmer et al., 2004). However, similar beneficial effects on emotional processing may not be seen with acute administration of antidepressant drugs (Harmer, 2008).
Long term effects versus short term effects of antidepressant administration
Blunted emotions: Who am I?
The initial stages of treatment may increase emotional responses to threat related stimuli and anxiety levels may not decrease immediately (Harmer, 2008). Long term benefits of treatment are due to the downstream neuro-adaptive effects (Harmer, 2008). These include desensitisation of auto-receptors and down-regulation of postsynaptic serotonin receptors (Harmer, 2008). It is also theorised that the delay in the effectiveness of antidepressants is due to postponed expression of cellular action (Harmer, 2008). Another explanation may also be that antidepressants are not direct mood enhancers but rather affect the mechanisms of processing emotional stimuli, which only has beneficial consequences over time (Harmer, 2008). In accordance with this view, antidepressants have a bottom-up effect, and new life experiences are associated with a more positive bias which leads to improved mood (Harmer, 2008). Therefore, improvements in emotion may be linked to re-learning emotional associations (Harmer, 2008). The concept of re-learning has been thought to be associated with antidepressant induced synaptic plasticity (Manji et al., 2003).
In some cases, patients taking antidepressants report blunted and limited emotional responses (Price, Cole, & Goodwin, 2009). A study conducted by Price et al. (2009) investigated the experiences of blunted emotions in patients taking SSRIs. The study found that people experienced less intense emotions after the administration of SSRIs and that all their emotions seemed 'dulled', 'numbed', or 'flattened.' Some patients even reported feeling no emotion at all during treatment (Price, Cole, & Goodwin, 2009). Patients were however able to recognise and respond to emotional cues appropriately and had full control over there
emotions (Price, Cole, & Goodwin, 2009). Positive emotions were reduced by most patients whereas negative emotions were reduced by all patients, the latter being more beneficial and outweighing the negative effect on positive emotions (Price, Cole, & Goodwin, 2009). Emotional detachment was also experienced by most patients and they described it as feeling as if they were in a 'limbo' of 'unreality' (Price, Cole, & Goodwin, 2009). These feelings were associated with emotional detachment from family, friends and partners (Price, Cole, & Goodwin, 2009). Another consequence of antidepressant treatment was that patients reported feelings of not caring for themselves or others and a loss of self-identity (Price, Cole, & Goodwin, 2009).
Antidepressants have many beneficial aspects in the regulation of
emotions to help improve the quality of life for those suffering from depression. It is possible that people using these medications adapt to form more positive schemas and biases. There are some possible negative side effects of the treatment, such as early increases in anxiety and blunted emotions which may negatively impact individuals. The chapter has briefly covered the major effects of antidepressants on emotions however, a much broader scope exists. The differences between treatments for their effects on emotion has not yet been determined and may be a useful topic for further research in this field.
Depression and motivation (Book Chapter, 2010)
Depression and motivation (Book Chapter, 2014)
Self-esteem and depression (Book Chapter, 2014)
Depression in older adults (Book Chpater, 2015)
Trans-cranial direct current stimulation and depression (Book Chapter, 2015)
Depression in adolescence (Book Chapter, 2015)
Norepinephrine and emotional disorders (Book Chapter, 2015)
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Plitchik's wheel of emotion}}