Developing in the late 1960s, heavy psych was a product of the nebulous Psychedelic Rock era, taking trends from the flourishing Blues Rock scene such as heavy dependence on riffs and willingness to improvise, adding crushing levels of heaviness with thick fuzzy guitars, creating a more doomy and morose atmosphere. Songs tend to be long, are often instrumental or have little vocals, tempos are often slow or mid-paced, and may have improvised sections with long solos drawing influence from the blues rock style.

The most direct origins of heavy psych can be traced to Cream and especially The Jimi Hendrix Experience's first album Are You Experienced with heavy emphasis on riffs with thick guitar and bass sound, sound effects and manipulation, and long solos. The first heavy psych bands like Blue Cheer and Vanilla Fudge went on to use these traits extensively, with Blue Cheer especially known for their sheer heaviness. Developing in the late 60s, there was a large deal of overlap with other rock styles developing at the same time, particularly it's sister genre Hard Rock, which many of the more bluesy bands most resembled. At the same time many groups took on Progressive Rock tendencies which makes sense considering both genres came from similar origins and thus the willingness of both to escape basic song structures, the most known of this type of heavy psych would be T2, Captain Beyond, and High Tide.

Heavy psych is considered by some to be the bridge between blues and psychedelic rock to Heavy Metal, and there is definite merit to the idea, with both having emphasis on heaviness and loudness and a more depressive atmosphere, and several bands would be not just an influence to heavy metal but also Traditional Doom Metal, such as Randy Holden and Flower Travellin' Band with some of the heaviest guitars yet and slow, non-groovy riffs ushering in a new era in heavy rock.

Heavy psych was never a concrete scene, but a specific sound created by multiple different bands across the world. It was almost completely an underground sound with many bands being "one-and-dones", and mostly all having relatively short careers known mostly by only enthusiasts of the time period. This style was most prevalent in the early 1970s, and was nearly completely dead by the time of the Punk Rock explosion. That isn't the end of heavy psych's story though, as the Stoner Rock and Stoner Metal scene was very much influenced by a lot of the psych groups, particularly the heaviest bands of the bunch, such as the aforementioned Blue Cheer along with Buffalo, and Sir Lord Baltimore, these bands themselves being a part of the original heavy metal sound. With the stoner rock scene becoming ever more popular since the early 90s, a number of bands have emerged with a sound that is consistent to the original heavy psych canon, with different groups taking different influences, such as stoner rock cyclically influencing psych (Colour Haze, Witch), Space Rock (Monster Magnet), traditional doom metal (Uncle Acid & The Deadbeats), and Garage Rock (Fuzz).experimentation of psychedelia.