I haven't owned a TV in almost 20 years. I don't miss it at all.
Note that I didn't say I don't watch TV. I and everyone I know does.
TV is everywhere these days: your phone; the internet; public spaces; download & watch it on your computer. The only real changes are the increased ease of time shifting (choosing when we watch), placeshifting (where we watch), and largely optional advertising.
Is TV Relaxing?
Yes, but not in the way you'd expect.
Robert Kubey and Mihaly Csikszentmihalyi did a study which appeared in Scientific American in 2002. Participants carried a beeper which beeped several times a day and when it did, they wrote down what they were doing and how they were feeling.
When beeped while watching TV, people recorded feeling relaxed and passive. What was surprising was that the relaxation ended as soon as the TV was switched off, but the feelings of passivity and lowered alertness continued.
Additionally, the participants had more trouble concentrating after viewing than before, and EEG studies showed less mental stimulation (identified by increased alpha brain wave production) while watching TV. Neither occurrences happened as a result of plain old reading.
In other words, we associate "watching TV" with "being relaxed" (so we do relax), but after we finish watching we can't concentrate, feel sluggish, and become as stressed (or more so) than before.
Despite all this, of course, we keep on watching.
IS TV ADDICTIVE?
Substance dependence is defined (very roughly, it's a big subject) as: spending a lot of time using the substance; tendency to increase the dose (using more than you planned); a psychological or physical dependence on the effects of the substance; a desire to continue using the substance for the sense of improved well-being it creates; giving up social, family or work activities to use it; experiencing withdrawal symptoms when you stop using it.
Not all addictions are chemical, of course. Any behavior that leads to a pleasurable experience will be repeated, especially if that behavior requires little effort. The psychological term for this is "positive reinforcement."
Two experiments were conducted where people were asked to stop watching television. In the first, South African families agreed to switch off for a month. The poorest family gave up after a week, others suffered from depression, saying they "felt like they had lost a friend." In the second, 182 West Germans agreed to avoid TV for a year (with the added bonus of payment). None lasted more than six months, and all of the participants showed increased anxiety, frustration and depression. Yes, the exact symptoms of heroin withdrawal.
In order to understand television addiction, it's important to note what is happening inside our brains.
When you watch TV, brain activity switches from the left to the right hemisphere. How much? Research by Professor Herbert Krugman showed that the right hemisphere becomes twice as active as the left, an extreme neurological anomaly.
The crossover from left to right releases a surge of endorphins, which include beta-endorphins (pain numbing) and enkephalins. Endorphins are structurally identical to opium and its derivatives (morphine, codeine, heroin, etc.). Activities that release endorphins (also called opioid peptides) are usually habit-forming. External opiates act on the same receptor sites (opioid receptors) as endorphins, so there is little difference between the two.
There are further implications of the left-to-right hemisphere blood flow effect.
Further research by Krugman revealed that our brain’s left hemisphere, which processes information logically and analytically, tunes out while we are watching television. The left hemisphere is the critical region for organizing, analyzing, and judging incoming data. This tuning-out allows the right hemisphere of our brain, which processes information emotionally and uncritically, to function unimpeded.
In other words, we switch off our critical thinking abilities and just absorb anything thrown at us. We watch emotionally, not intelligently.
Further to this, psychophysiologist Thomas Mulholland found that after just 30 seconds of watching television the brain begins to produce alpha waves, which indicates torpid (almost comatose) rates of activity. Alpha brain waves are associated with unfocused, overly receptive states of consciousness (as with the left-to-right hemisphere shift). High frequency alpha waves do not normally occur when the eyes are open. In fact, Mulholland’s research implies that watching television is neurologically analogous to staring at a blank wall.
Production of alpha waves and the subsequent receptive state are also the goal of hypnotists. They're both present during the "light hypnotic" state used by hypno-therapists for suggestion therapy.
Of course, when this research came out the advertising industry jumped all over it. Marketers began designing commercials that were utterly irrational (since that part of the brain is switched off) but intended to implant moods that the consumer will then associate with a given product. Endorsements from athletes and celebrities are great for this.
TV ISN'T REAL (BUT WE DON'T KNOW THAT)
Some other interesting things happen in the brain while we're watching television.
The higher brain regions (the midbrain/neo-cortex, ie "cognitive parts") are shut down, and most activity shifts to the lower brain regions (the limbic system, our "reptilian brain"). Our limbic system controls our very basic "fight or flight" response.
Researcher Jacob Jacoby found that, out of 2,700 people he tested, 90% misunderstood what they had watched on television only minutes before. That's what happens when our higher brain functions are switched off.
Furthermore, the limbic system can't tell the difference between something we're watching, and reality. Anything we see in front of us is real to our vestigial reptile brain. Identifying the difference between reality and fiction is a job performed by the neo-cortex (which is off, remember).
What it all means is this: With our neo-cortex out of the picture, our limbic system then reacts to TV as if it were real, and releases the appropriate fight/flight hormones (with the concurrent stresses that places on the body). Add to that, longitudinal studies have shown that extended lower brain activity leads to higher brain atrophy. The more TV we watch, the poorer our cognitive brain functions.
In other words, too much TV makes us stupider and more emotionally reactive, more animalistic.
TV IS worse than you think
In summary: It's highly addictive, makes us docile (without actually relaxing us), stresses us as if we experience everything we see, makes it harder for us to concentrate and over time really does make us stupider.
I'm sure this is all of little surprise.
Will it stop me watching? Probably not (see also: opiate addict).
However, I sure as hell am going to be a lot more discriminatory in what I choose to watch. While I'm watching TV, my brain is passively absorbing 1800 pictures a minute (ie, 40,000 pictures in a half hour show, along with all the emotion). I like my brain, thank you, and would prefer more of a say over what's inside it.
As a starting point, I'm going to stop watching visual media (except in social situations — don't need to become a pariah) for at least a month. It should be an interesting mini-experiment.
 T.Mulholland. The concept of attention and the electroencephalographic alpha rhythm. In Attention in Neurophysiology, eds C. Evans and T.Mulholland. London, Butterworths, 1969, 100–127. [no online doc available]