Navigation Links
Why serotonin can cause depression and anxiety

Mood disorders could be caused by a loss of our inherent, reflexive avoidance of aversive events, according to a study published in PLoS Computational Biology. Researchers from UCL in London and Columbia University in New York used computational modeling techniques to integrate what appeared to be blatant contradictions between serotonins roles in different states of health.

Serotonin appears to be one of the major players in mood and a variety of other disorders. But exactly how remains an open question. Imagine walking past a dark alleyway in a dangerous part of some city; although it might be a shortcut, most people wouldnt consider taking it. In healthy subjects, serotonin appears important for this automatic avoidance.

It has long been suggested that over-activity of the serotonin system may relate to mood disorders such as depression and anxiety, as these seem characterized by too much withdrawal and avoidance. However, the new modeling study simply suggests that we think about what happens when these reflexes failsuddenly you have to think hard to avoid things that used to be avoided reflexively You might for example consider walking down the dangerous alley, be robbed and thus be reminded and taught by additional experience that dark alleys are to be avoided.

In this study Prof. Peter Dayan and Dr. Quentin Huys built a reinforcement learning model of reflexive choices. Agents take actions and as a result of these move through a set of states, some of which are rewarded or punished. As agents progress through this space, they learn the value of each statehow much punishment or reward is to be expected from this state onwards.

It turns out that adding to the agents behavioural repertoire a simple reflex, which guides the agent away from an action with potential for poor consequences, does two things: it increases the rewards reaped overall, but, because bad states are now not explored any more, it also prevents them from learning exactly how bad these bad states are. When serotonin drops, say in depression or anxiety, agents have no more recourse to the reflexive avoidance and have to rely on what they learned. Because they have not learned how bad the bad states are, they start exploring states that dont look too bad to them, but in reality are much worse. Serotonin enhancing drugs, such as Prozac, are then suggested to reinstate the reflexive avoidance, and thus to redress the balance.

This study gives insight into some puzzling findingsfor example, it argues that the association of depression with aggression may have to do with a lack of reflexive avoidance of it. In addition, stress not only causes depression, but people with depression experience more stressors. Again, this may be related to a dysfunctional reflexive avoidance system. The study, however, vastly oversimplifies a number of issues, such as the flexibility of reflexive actions, and the effect of non-reflexive action choice. These provide interesting avenues for further research, and may in fact give some insight into the co-morbidity of different mood disorders.


Contact: Mary Kohut
Public Library of Science

Related biology news :

1. Women more depressed and men more impulsive with reduced serotonin functioning
2. deCODE discovers cause of major subtype of glaucoma
3. Study begins to reveal clues to the cause and progression of sepsis
4. Bleeding, not inflammation, is major cause of early lung infection death
5. Gamma globulin effective in treating eye infections caused by adenoviruses
6. Hidden interactions between predators and prey: evolution causes cryptic dynamics in ecology
7. Spaceflight shown to alter ability of bacteria to cause disease
8. Grubs passion for plastic causes water loss
9. Human embryonic stem cells remain embryonic because of epigenetic factors
10. Salmonid hatcheries cause stunning loss of reproduction
11. Researchers find evidence linking stress caused by the Sept. 11 disaster with low birth weights
Post Your Comments:
(Date:11/4/2015)... 2015 --> ... by Transparency Market Research "Home Security Solutions Market - Global ... - 2022", the global home security solutions market is expected to ... The market is estimated to expand at a CAGR ... 2022. Rising security needs among customers at homes, the ...
(Date:10/29/2015)... 2015   MedNet Solutions , an innovative SaaS-based ... clinical research, is pleased to announce that it has ... as one of only three finalists for a ... and Growing" category. The Tekne Awards honor Minnesota ... technology innovation and leadership. iMedNet™ eClinical ...
(Date:10/29/2015)... 29, 2015 Daon, a global leader in ... released a new version of its IdentityX Platform ... North America have already installed IdentityX v4.0 ... a FIDO UAF certified server component as ... activate FIDO features. These customers include some of the ...
Breaking Biology News(10 mins):
(Date:11/30/2015)... interventional radiology technique shows promise for helping morbidly obese patients ... being presented today at the annual meeting of the Radiological ... --> --> Gastric artery ... a way to stop bleeding in emergency situations, but the ... obesity is new. Mubin Syed , M.D., interventional ...
(Date:11/30/2015)... 30, 2015 Harvard Apparatus Regenerative Technology, ... company developing bioengineered organ implants for life-threatening conditions, ... The NASDAQ Stock Market that it has regained ... letter noted that as a result of the ... exceeded $1.00 per share for more than ten ...
(Date:11/30/2015)... Nov. 30, 2015  Champions Oncology, Inc. (CSBR), engaged ... to personalize the development and use of oncology drugs, ... Officer, will be presenting at the LD MICRO Investor ... Standard Time (PST).  The conference, held at the Luxe ... CA , will feature 200 small/micro-cap companies and ...
(Date:11/30/2015)... -- Aytu BioScience, Inc. (OTCQB: AYTU), a commercial-stage specialty healthcare ... at two upcoming investor conferences. Aytu is scheduled to ... to be held December 3, 2015, and at LD ... 2 nd & 3 rd , 2015 in ... via webcast. Josh Disbrow , Chief Executive ...
Breaking Biology Technology: