Yes and no. An espresso cup has about as much caffeine as a cup of dark brew. But servings for espresso are much smaller. Which means that the content of caffeine per millilitre are much higher than with a regular brew. Moreover, caffeine is more quickly assimilated when taken in concentrated dosages, such as an espresso cup.
The myth of lower caffeine espresso comes comes from the fact that the darker roast beans used for espresso do have less caffeine than regularly roasted beans as roasting is supposed to break up or sublimate the caffeine in the beans (I have read this quote on research articles, but found no scientific studies supporting it. Anybody out there?). But espresso is prepared using pressurized water through significantly more ground (twice as much?) than regular drip coffee, resulting in a higher percentage of caffeine per millilitre.
Here's the caffeine content of Drip/Espresso/Brewed Coffee:
| Drip | 115-175 | |
| Espresso | 100 | 1 serving (1.5-2oz) |
| Brewed | 80-135 |