Recent advances in the psychopharmacology of social phobia

Anxiety and depression: individual entities or two sides of the same coin?

Several factors have led to suggestions that anxiety and depression are actually the same disease: very frequently, they co-exist; there is an overlap of symptoms between the two conditions; a number of similar agents can be used to treat both mental states; the same neurotransmitters are involved in both anxiety and depressive disorders; and stress can predispose both. Selective serotonin reuptake inhibitors (SSRIs) have shown efficacy in a number of neuroses: depression; obsessive-compulsive disorder (OCD) and anxiety disorders (panic disorder [PD], social anxiety disorder [SAD], generalised anxiety disorder and post-traumatic stress disorder). Furthermore, other drugs, for example, tricyclic antidepressants and monoamine oxidase inhibitors, are effective in treating both depression and some anxiety disorders. Yet some drugs are only effective in anxiety, for example, benzodiazepines, and this suggests that the two states are actually different. Despite the broad range of conditions that are treated by SSRIs, a number of differences are clear when SSRIs are used in depressive and anxious states. When used in PD and OCD, the effective dose of the SSRI is often higher than when used to treat depression. Furthermore, SSRIs often work more slowly in patients with anxiety compared with those with depression. In order to assess which serotonergic pathways and mechanisms are involved in these conditions, tryptophan depletion tests can be performed. Tryptophan is the precursor to serotonin (5-HT), so if the SSRI treatment effects are dependent on an increase in synaptic 5-HT levels, depletion will result in a relapse in symptoms. However, if the SSRI treatment works through post-receptor events, then tryptophan depletion will have little effect on the individual's symptoms. In depression, tryptophan depletion induced relapse in patients treated and controlled on SSRIs, but not in those recovered on noradrenergic agents such as desipramine. In some anxious states (PD and SAD), our work has shown that relapse was also experienced following tryptophan depletion, indicating that the SSRIs are acting via increasing 5-HT levels at the synapse in these conditions. However, other studies have found no effect of the tryptophan depletion test. This suggests that in OCD, SSRIs act post-synaptically and therefore have a different mechanism of action in OCD patients compared with depressed patients. In summary, although most SSRIs are effective in the treatment of both depression and anxiety, differences in dose, time to onset of action and, in some cases, mechanism of action are evident when treating the two conditions.

The clinical relevance of treating social phobia

Social phobia is an extreme fear of being scrutinized by others in social situations that often culminates in avoidance of those situations. Studies have demonstrated marked educational, occupational and social disabilities in patients with social phobia. However, many sufferers do not seek help and are not detected when seeking medical advice for other conditions. The advent of a range of effective treatments, in particular the selective serotonin reuptake inhibitors, has substantially improved the prognosis in these sufferers, both symptomatically and in terms of quality of life.

Serotonin uptake inhibitors: uses in clinical therapy and in laboratory research

Fluoxetine, zimelidine, sertraline, paroxetine, fluvoxamine, indalpine and citalopram are the selective inhibitors of serotonin uptake that have been most widely studied. Some of these compounds are or have been used clinically in the treatment of mental depression, obsessive-compulsive disorder and bulimia, and therapeutic benefit has been claimed in additional diseases as well. By blocking the membrane uptake carrier which transports serotonin from the extracellular space to inside the serotonin nerve terminals, these compounds increase extracellular concentrations of serotonin and amplify signals sent by serotonin neurons. Because serotonin neurons are widespread in the central nervous system, the functional consequences of blocking serotonin uptake are diverse, but are generally subtle. Animals treated with serotonin uptake inhibitors look normal in gross appearance, but effects such as reduced aggressive behavior, decreased food intake and altered food selection, analgesia, anticonvulsant activity, endocrine changes and neurochemical changes have been demonstrated and characterized. Serotonin uptake inhibitors have helped in revealing some dynamics of serotonin neurons; for example, when uptake is inhibited and extracellular serotonin concentration increases, presynaptic as well as postsynaptic receptors for serotonin are activated to a greater degree. A consequence of increased activation of autoreceptors on serotonin cell bodies and nerve terminals is a reduction in firing of serotonin neurons and a decrease in serotonin synthesis and release. The result is a limit on the degree to which extracellular serotonin and serotonergic neurotransmission are increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Psychopharmacological treatment of social phobia; a double blind placebo controlled study with fluvoxamine

Previous studies have shown selective and nonselective monoamine oxidase inhibitors (MAOIs) to be effective in the treatment of social phobia. In this study we investigated the efficacy of selective serotonin reuptake inhibitors (SSRIs) in social phobia. Thirty patients with social phobia (DSM-IIIR) were treated with the SS-RI fluvoxamine (150 mg daily) using a 12-week double-blind placebo controlled design. A substantial improvement was observed in seven (46%) patients on fluvoxamine and in one (7%) on placebo. Statistically significant effects were seen on measures of social anxiety and general (or anticipatory) anxiety in patients treated with fluvoxamine compared with placebo. The level of phobic avoidance decreased also but the difference at endpoint between fluvoxamine and placebo failed to reach statistical significance. It is concluded that treatment with the SSRI fluvoxamine has beneficial effects in patients suffering from social phobia, suggesting that serotonergic mechanisms might be implicated in social anxiety.